2012 KDIGO：CKD评估与管理临床实践指南

指南肾脏内科· 其他肾脏疾病 · 2013

Criteria for CKD

Defining terms: The following section aims to define specific terms and concepts so as to ensure clarity among all users. In addition, the rationale for including these terms is included.

Table 3 provides a justification for the criteria for CKD. The criteria for definition of CKD are objective and can be ascertained by means of simple laboratory tests without identification of the cause of disease, thereby enabling detection of CKD by non-nephrologist physicians and other health professionals.

Duration 43 Months

Kidney diseases may be acute or chronic. We explicitly but arbitrarily define duration of 43 months (490 days) as delineating ''chronic'' kidney disease. The rationale for defining chronicity is to differentiate CKD from acute kidney diseases (such as acute GN), including AKI, which may require different interventions, and have different etiologies and outcomes. 7 We did not define acute kidney disease (AKD) because there does not appear be an evidence base for a precise definition.

The duration of kidney disease may be documented or inferred based on the clinical context. For example, a patient with decreased kidney function or kidney damage in the midst of an acute illness, without prior documentation of kidney disease, may be inferred to have AKI. Resolution over days to weeks would confirm the diagnosis of AKI. A patient with similar findings in the absence of an acute illness may be inferred to have CKD, and if followed over time would be confirmed to have CKD. In both cases, repeat ascertainment of kidney function and kidney damage is recommended for accurate diagnosis. The timing of the evaluation depends on clinical judgment, with earlier evaluation for the patients suspected of having AKI and later evaluation for the patient suspected of having CKD. For further details on the Evaluation of CKD, see Chapter 1. 4.

Reversibility. Most kidney diseases do not have symptoms or findings until later in their course and are detected only when they are chronic. Most causes of CKD are irreversible with a life-long course, and treatment aimed at slowing progression to kidney failure. However, chronicity is not synonymous with irreversibility. In some cases, CKD is entirely reversible, either spontaneously or with treatment, and in other cases, treatment can cause partial regression of kidney damage and improvement in function (e.g., immunosuppressive therapies for GN). Even kidney failure may be reversed with transplantation. Because of the long course of most cases of CKD, patients often have one or more episodes of AKI, superimposed upon CKD.

Decreased GFR

The kidney has many functions, including excretory, endocrine and metabolic functions. The GFR is one component of excretory function, but is widely accepted as the best overall index of kidney function because it is generally reduced after widespread structural damage and most other kidney functions decline in parallel with GFR in CKD.

We chose a threshold of GFR o60 ml/min/1.73 m 2 (GFR categories G3a-G5) for 43 months to indicate CKD. A GFR o60 ml/min/1.73 m 2 is less than half of the normal value in young adult men and women of approximately 125 ml/min/ 1.73 m 2 . Figure 2 shows a compilation of GFR measurements in apparently healthy men and women in the US and Europe by age from more than 40 years ago. 20 The age-associated GFR decline is observed in longitudinal as well as cross Duration is necessary to distinguish chronic from acute kidney diseases K Clinical evaluation will often enable documentation or inference of duration K Documentation of duration is usually not declared in epidemiologic studies GFR o60 ml/min/1.73 m 2 (GFR categories G3a-G5) GFR is the best overall index of kidney function in health and disease K The normal GFR in young adults is approximately 125 ml/min/1.73 m 2 .m 2 (GFR category G5) is defined as kidney failure K Decreased GFR can be detected by current estimating equations for GFR based on SCr or cystatin C but not by SCr or cystatin C alone K Decreased eGFR can be confirmed by measured GFR, if required Kidney damage as defined by structural abnormalities or functional abnormalities other than decreased GFR Albuminuria as a marker of kidney damage [increased glomerular permeability], urine AER Z30 mg/24 hours, approximately equivalent to urine ACRZ30 mg/g (Z3 mg/mmol)* K The normal urine ACR in young adults is o10 mg/g (o1 mg/mmol) K Urine ACR 30-300 mg/g (3-30 mg/mmol; category A2) generally corresponds to ''microalbuminuria,'' now referred to as ''moderately increased'' K Urine ACR 4300 mg/g (430 mg/mmol; category A3) generally corresponds to ''macroalbuminuria,'' now termed ''severely increased'' K Urine ACR42200 mg/g (220 mg/mmol) may be accompanied by signs and symptoms of nephrotic syndrome (e. GFR o15 ml/min/1.73 m 2 (GFR category G5) is defined as kidney failure K Decreased GFR can be detected by current estimating equations for GFR based on SCr or cystatin C but not by SCr or cystatin C alone K Decreased eGFR can be confirmed by measured GFR, if required Kidney damage as defined by structural abnormalities or functional abnormalities other than decreased GFR Albuminuria as a marker of kidney damage [increased glomerular permeability], urine AER Z30 mg/24 hours, approximately equivalent to urine ACRZ30 mg/g (Z3 mg/mmol)* K The normal urine ACR in young adults is o10 mg/g (o1 mg/mmol) K Urine ACR 30-300 mg/g (3-30 mg/mmol; category A2) generally corresponds to ''microalbuminuria,'' now referred to as ''moderately increased'' K Urine ACR 4300 mg/g (430 mg/mmol; category A3) generally corresponds to ''macroalbuminuria,'' now termed ''severely increased'' K Urine ACR42200 mg/g (220 mg/mmol) may be accompanied by signs and symptoms of nephrotic syndrome (e.g., low serum albumin, edema, and high serum cholesterol) K Threshold value corresponds approximately to urine reagent strip values of trace or +, depending on urine concentration. K High urine ACR can be confirmed by urine albumin excretion in a timed urine collection expressed as AER Urinary sediment abnormalities as markers of kidney damage K Isolated non-visible (microscopic) hematuria with abnormal RBC morphology (anisocytosis) in GBM disorders K RBC casts in proliferative glomerulonephritis K WBC casts in pyelonephritis or interstitial nephritis K Oval fat bodies or fatty casts in diseases with proteinuria K Granular casts and renal tubular epithelial cells in many parenchymal diseases (non-specific) c h a p t e r 1 sectional studies, but varies substantially among individuals within the population. 21 More recent data in kidney donors confirm these general trends. 22, 23 ] [26] A GFR o60 ml/min/1.73 m 2 can be detected by routine laboratory testing. Current estimating equations for GFR (eGFR) based on serum creatinine (SCr), but not SCr alone, are sensitive for detecting measured GFRo60 ml/min/ 1.73 m 2 . 27 A decreased eGFR using SCr can be confirmed by GFR estimation using an alternative filtration marker (cystatin C) or GFR measurement, as necessary.

A GFRo60 ml/min/1.73 m 2 is associated with a higher risk of complications of CKD than in subjects with CKD and conserved GFR. The causal mechanisms underlying these associations are not fully understood. We consider three main types of complications, which are of relevance to all patients with CKD and reduced GFR, irrespective of country, age or etiology:

Drug toxicity. Altered pharmacokinetics of drugs excreted by the kidney and an increased risk of drug-interactions are common and require adjustment in the dosage of many drugs (see Chapter 4.4). 13 At lower GFR, altered pharmacokinetics and pharmacodynamics of drugs not excreted by the kidney may also be observed. Errors in drug dosing are common in patients with CKD and may be associated with toxicity to the kidney (resulting in AKI) or systemic toxicity, resulting in threats to patient safety.

Metabolic and endocrine complications. As GFR declines a variety of complications reflecting loss of endocrine or exocrine function of the kidneys develop including anemia, acidosis, malnutrition, bone and mineral disorders (described in Chapters 3 and 4).

Risk of CVD and death.

A meta-analysis by the CKD Prognosis Consortium demonstrated associations of eGFR o60 ml/ min/1.73 4] [5] Figure 3 shows the relationship for total and cardiovascular mortality in general population cohorts. The risk for all outcomes was relatively constant between eGFR of 75-105 ml/min/1.73 m 2 , with a suggestion of a U-shaped curve for total mortality. The increased relative risk (RR) for all outcomes was significant for eGFR of o60 ml/min/1.73 m 2 .

Kidney Damage

Damage to the kidney can be within the parenchyma, large blood vessels or collecting systems, and is most often inferred from markers rather than direct examination of kidney tissue. The markers of kidney damage often provide a clue to the likely site of damage within the kidney and in association with other clinical findings, the cause of kidney disease.

Proteinuria. Proteinuria is a general term for the presence of increased amounts of protein in the urine. Proteinuria may reflect abnormal loss of plasma proteins due to a) increased glomerular permeability to large molecular weight proteins (albuminuria or glomerular proteinuria), b) incomplete tubular reabsorption of normally filtered low-molecularweight proteins (tubular proteinuria), or c) increased plasma concentration of low-molecular-weight proteins (overproduction proteinuria, such as immunoglobulin light chains). Proteinuria may also reflect abnormal loss of proteins derived from the kidney (renal tubular cell constituents due to tubular damage) and lower urinary tract. Albuminuria, tubular proteinuria and renal tubular cell constituents are pathognomonic of kidney damage. In addition, findings from experimental and clinical studies have suggested an important role for proteinuria in the pathogenesis of disease progression of CKD. 28 lbuminuria. Albuminuria refers to abnormal loss of albumin in the urine. Albumin is one type of plasma protein found in the urine in normal subjects and in larger quantity in patients with kidney disease.

For a number of reasons, clinical terminology is changing to focus on albuminuria rather than proteinuria: a) albumin is the principal component of urinary protein in most kidney diseases; recent recommendations for measurement of urine proteins emphasize quantification of albuminuria rather than total protein; b) recent epidemiologic data from studies around the world demonstrate a strong graded relationship of the quantity of urine albumin with both kidney and CVD risk; and c) later recommendations in these guidelines classify kidney disease by level of albuminuria. In this guideline, we will refer to proteinuria when discussing general concepts and will refer either to total protein, albumin or other specific proteins when discussing measurements, patterns, and interpretation of proteinuria.

Albuminuria is a common but not uniform finding in CKD. It is the earliest marker of glomerular diseases, including diabetic glomerulosclerosis, where it generally appears before the reduction in GFR. It is a marker of hypertensive nephrosclerosis but may not appear until after the reduction in GFR. It is often associated with underlying hypertension, obesity, and vascular disease, where the underlying renal pathology is not known.

Normative values for albuminuria and proteinuria are generally expressed as the urinary loss rate. The urinary loss rate of albumin and protein has commonly been referred to as AER and protein excretion rate (PER), respectively, although in the strict physiological sense they are not excreted. The terms AER and PER will be retained herein.

We chose a threshold for urinary AER of Z30 mg/ 24 hours sustained for 43 months to indicate CKD. This value is considered to be approximately equivalent to an ACR in a random untimed urine sample of Z30 mg/g or Z3 mg/mmol. The rationale for this threshold is as follows:

K An AER of Z30 mg/24 hours (ACRZ30 mg/g [Z3 mg/ mmol]) is greater than 3 times the normal value in young adult men and women of approximately 10 mg/24 hours (ACR 10 mg/g or 1 mg/mmol).

K An AER of Z30 mg/24 hours (ACRZ30 mg/g [Z3 mg/ mmol]) may sometimes be detectable as 'trace' using a urine reagent strip, depending on urine concentration, but this is not a consistent finding until AER exceeds approximately 300 mg/24 hours (ACRZ300 mg/g [Z30 mg/mmol] ). As described later, trace or positive reagent strip values/readings can be confirmed by ACR, and an elevated ACR can be confirmed by urine AER in a timed urine collection, as necessary.

K An AERZ30 mg/24 hours (ACRZ30 mg/g [Z3 mg/ mmol]) is associated with an increased risk for complications of CKD. A meta-analysis by the CKD Prognosis Consortium demonstrated associations of an ACRZ30 mg/g (Z3 mg/mmol) or reagent strip 1 þ protein with subsequent risk of all-cause and cardiovascular mortality, kidney failure, AKI, and CKD progression in the general population and in populations with increased risk for CVD [3] [4] [5] (Figure 4 ). Urine sediment abnormalities. Formed elements, such as cells, casts, crystals, and microorganisms may appear in the urine sediment in a variety of disorders of the kidney and urinary tract, but renal tubular cells, red blood cell (RBC) casts, white blood cell (WBC) casts, coarse granular casts, wide casts, and large numbers of dysmorphic RBCs are pathognomonic of kidney damage.

Electrolyte and other abnormalities due to tubular disorders.

Abnormalities of electrolytes and other solutes may result from disorders of renal tubular reabsorption and secretion. These syndromes are uncommon but pathognomonic of kidney disease. Often the diseases are genetic without underlying pathologic abnormalities. Other diseases are acquired, due to drugs or toxins, and are usually with prominent tubular pathologic lesions.

Pathologic abnormalities directly observed in kidney tissue

obtained by biopsy. Evidence of abnormalities of renal parenchyma in kidney biopsies irrespective of eGFR or other markers of kidney damage must be acknowledged as an important parameter in defining kidney damage. The pathologic classification of diseases of the renal parenchyma reflects the localization of the disease to glomeruli, vessels, tubules and interstitium, or cysts. Renal biopsies are performed in the minority of CKD patients.

Imaging abnormalities. Imaging techniques allow the diagnosis of diseases of the renal structure, vessels and/or collecting systems. Thus, patients with significant structural abnormalities are considered to have CKD if the abnormality persists for greater than 3 months (note that this does not include simple cysts and clinical context is required for action).

History of kidney transplantation. Kidney transplant recipients are defined as having CKD, irrespective of the level of GFR or presence of markers of kidney damage. The rationale Figure 3 | Relationship of eGFR with mortality. HRs and 95% CIs for all-cause (a) and cardiovascular mortality (c) according to spline eGFR. HRs and 95% CIs (shaded areas) are adjusted for ACR, age, sex, ethnic origin, history of CVD, systolic BP, diabetes, smoking, and total cholesterol. The reference (diamond) was eGFR 95 ml/min/1.73 m 2 and ACR 5 mg/g (0.6 mg/mmol), respectively. Circles represent statistically significant and triangles represent not significant. ACR, albumin-to-creatinine ratio; BP, blood pressure; CI, confidence interval; CVD, cardiovascular disease; eGFR, estimated glomerular filtration rate; HR, hazard ratio. Reprinted from The Lancet, vol 375, Matshushita K, van de Velde M, Astor BC, et al. 4 Association of estimated glomerular filtration rate and albuminuria with all-cause and cardiovascular mortality in general population cohorts: a collaborative meta-analysis, p. 2073-2081, 2010, with permission from Elsevier; accessed http:// download.thelancet.com/pdfs/journals/lancet/ PIIS0140673610606745.pdf Figure 4 | Relationship of albuminuria with mortality. HRs and 95% CIs for all-cause (b) and cardiovascular mortality (d) according to ACR. HRs and 95% CIs (shaded areas) are adjusted for age, sex, ethnic origin, history of CVD, systolic BP, diabetes, smoking, and total cholesterol and spline eGFR. The reference (diamond) was ACR 5 mg/g (0.6 mg/mmol) and eGFR 95 ml/min/ 1.73 m 2 , respectively. Circles represent statistically significant and triangles represent not significant. ACR plotted in mg/g. To convert ACR in mg/g to mg/mmol multiply by 0.113. Approximate conversions to mg/mmol are shown in parentheses. ACR, albumin-to-creatinine ratio; BP, blood pressure; CI, confidence interval; CVD, cardiovascular disease; eGFR, estimated glomerular filtration rate; HR, hazard ratio. Reprinted from The Lancet, vol 375, Matshushita K, van de Velde M, Astor BC, et al. 4 Association of estimated glomerular filtration rate and albuminuria with all-cause and cardiovascular mortality in general population cohorts: a collaborative meta-analysis, p. 2073-2081, 2010, with permission from Elsevier; accessed http://download.thelancet.com/pdfs/ journals/lancet/PIIS0140673610606745.pdf c h a p t e r 1 for this designation is that biopsies in kidney transplant recipients reveal pathologic abnormalities even in patients without decreased GFR or albuminuria. Kidney transplant recipients have an increased risk of mortality and kidney outcomes compared to the general population and they require specialized medical management. 29

Implications for Health

CKD is associated with a wide range of complications leading to adverse health outcomes. For some complications, the causal pathway between kidney disease and adverse outcomes is well-known. For these complications, there are clinical practice guidelines for testing and treatment for modifiable factors to prevent adverse outcomes. Since 2002 a large number of epidemiologic studies have linked decreased GFR and albuminuria to the risk of adverse health outcomes not previously identified as CKD complications. The exploration of the mechanisms for the relationships of CKD with these complications is a rapidly growing topic for basic and clinical research. Because of the high prevalence, adverse outcomes, and high cost of CKD, especially kidney failure, some countries have developed public health programs for early identification and treatment of CKD and its complications. The effectiveness of these programs is being evaluated.

Implications for Clinical Practice and Public Policy

CKD was first defined in the 2002 KDOQI Guidelines and endorsed at subsequent KDIGO Controversies Conferences with minor modifications. 30, 31 The definition of CKD proposed here is intended for use in clinical practice, research and public health, and has not changed. Thus, the updated version does not change any of the initiatives that have been commenced with respect to public policy. We recognize the variation around the world regarding measurement of urine albumin versus total protein in clinical practice, and we anticipate variation in implementation of the guideline until more widespread dissemination of the guideline has occurred. For additional discussion about methods for ascertainment of urine albumin versus total protein, see Recommendation 1.4.4 (Evaluation of albuminuria). The implications of highlighting the importance of albuminuria for general practitioners in evaluation and prognostication may help with identification and care planning. [34] [35] [36] Areas of Controversy, Confusion, or Non-consensus and Clarification of Issues and Key Points

General concerns:

a) The use of single thresholds without consideration of patient specific factors

The use of single thresholds to define decreased GFR and increased AER, without consideration for cause of disease, age, sex, race-ethnicity and clinical context is consistent with the use of single thresholds for disease markers to define other chronic non-communicable diseases, such as hyperten-sion, diabetes, and hypercholesterolemia, that primarily affect the elderly and are associated with an increased risk for cardiovascular mortality. Biologic variability and error in ascertainment of GFR and AER can lead to misclassification and false negative and false positive diagnosis. Furthermore, these single thresholds appear to differentiate groups of individuals and outcomes, irrespective of specific patient characteristics in a multitude of studies. However, they correspond to thresholds for RRs for complications, rather than predictions of absolute risk. Furthermore, as with any diagnostic tests, findings must be interpreted with considerations of likelihood of disease based on the clinical context but this should not negate the application of a standard definition for CKD.

Specific concerns: b) Relationship of CKD criteria to aging

Epidemiologic studies show an increased prevalence of decreased eGFR and increased ACR in older subjects. There has been vigorous debate as to whether decreased GFR or increased ACR in older people represent a disease or ''normal aging.'' Numerous studies show pathologic abnormalities associated with aging, including glomerular sclerosis, tubular atrophy and vascular sclerosis. ] [39] Irrespective of cause, there appears to be increased risk associated with decreased eGFR or increased ACR in older people, and for this reason, we consider all individuals with persistently decreased GFR or increased albuminuria to have CKD. Comparison of the magnitude of risk to younger individuals is complicated. 4] [5] Note is also made that healthy older individuals do not necessarily have decreased GFR, so that while one may expect some decline, levels below 60 ml/min/1.73 m 2 in individuals without comorbidity is the exception. 20

c) Isolated decreased GFR without markers of kidney damage

A variety of clinical circumstances are associated with GFR o60 ml/min/1.73 m 2 for 43 months in the absence of known structural alterations. Below are examples of these conditions and the rationale for considering them as CKD: K Heart failure, cirrhosis of the liver, and hypothyroidism.

Decreased GFR complicates the management of the primary disease and patients with these disorders with decreased GFR have a worse prognosis than those without decreased GFR. In addition, renal biopsy in these patients may reveal renal parenchymal lesions.

K Kidney donors. The usual level of GFR in kidney donors after transplantation is approximately 70% of the predonation level, in the range of 60-90 ml/min/1.73 m 2 in most donors. However, a minority of donors have GFR o60 ml/min/1.73 m 2 . The prognosis of these donors compared to those with higher GFR has not been carefully studied. However, as with decreased GFR due to recognized kidney diseases, donors with decreased GFR require closer follow-up for adjustment of drug doses.

K Malnutrition. The level of GFR is affected by habitual protein intake. 40 Healthy adults with lower protein intake may have lower mean GFR, but usually do not have GFR o60 ml/min/1.73 m 2 . Older studies of patients with protein-calorie malnutrition and more recent studies of subjects with anorexia nervosa have documented reduced measured GFR that can improve following restoration of nutritional status. However, renal biopsies may reveal structural abnormalities in these conditions and decreased GFR can complicate their management.

d) Isolated albuminuria without decreased GFR As described later, transient ACR Z30 mg/g (Z3 mg/ mmol) can occur in disorders other than CKD. Remission of albuminuria within 3 months in association with recovery from these disorders is not defined as CKD. Patients with persistent albuminuria would be considered to have CKD.

Below are examples of these conditions and the rationale for considering them as CKD:

K Obesity and metabolic syndrome. Albuminuria can be associated with obesity and metabolic syndrome, and can remit during weight loss. The mechanism of albuminuria in these conditions is not known but renal biopsies may reveal prominent vascular lesions. Patients with obesity and metabolic syndrome are at increased risk for development of diabetes and hypertension. The risk of persistent albuminuria in this condition has not been carefully studied.

K Orthostatic (postural) proteinuria. 41 Albuminuria may rarely be observed in the upright but not recumbent posture in patients with the syndrome of postural proteinuria. This condition is not associated with an increased risk of long-term adverse outcomes but a thorough evaluation is required to exclude other causes of CKD. Exclusion is generally possible by studying a first pass early morning urine (EMU) after overnight recumbency: total protein loss of 41000 mg/24 hours is unlikely to be explained by orthostatic proteinuria.

e) Remission of decreased GFR or markers of kidney damage

If decreased GFR and markers of kidney damage resolve while on treatment, the patient would be considered to have treated CKD, consistent with nomenclature for treated hypertension, treated diabetes, or treated hypercholesterolemia if blood pressure, blood glucose and blood cholesterol are within normal range while on medications. If resolution of decreased GFR and markers of kidney damage is sustained after withdrawal of treatment, the patient would be considered to have a history of CKD.

f) Kidney disease in the absence of decreased GFR and markers of kidney damage

A GFR Z60 ml/min/1.73 m 2 may reflect a decline from a higher value, and an AER of o30 mg/24 hours (ACR o30 mg/g or o3 mg/mmol) may reflect a rise from a lower value. Both findings may be associated with a pathologic process, even in the absence of other markers of kidney damage. Although such patients do not fulfill the criteria for CKD, a clinician's high index of suspicion may warrant additional diagnostic testing or close follow-up to detect the onset of CKD.

Pediatric Considerations

In general the definition of CKD in adults applies to children (birth-18 years) with the following exceptions or allowances:

K the criteria for duration 43 months does not apply to newborns or infants r3 months of age.

K the criteria of a GFR o60 ml/min/1.73 m 2 does not apply to children o2 years of age in whom an age appropriate value should be applied.

K a urinary total protein or albumin excretion rate above the normal value for age may be substituted for albuminuria Z30 mg/24 hours.

K all electrolyte abnormalities are to be defined in light of age normative values.

Developmental renal abnormalities account for as many as 30-50% of the children with CKD or ESRD. 42 As such many infants while born with normal SCr for age will in fact meet the definition of CKD based on structural abnormalities despite the appearance of a normal GFR and may be classified as such within the first few days of life.

Normal GFR in newborns is less than 60 ml/min/1.73 m 2 , and it is not until approximately 2 years of age that one expects to see body surface area (BSA) adjusted GFR values comparable to those seen in the adult. 43, 44 6] [47] [48] As such direct application of the GFR threshold values in the current CKD definition would not be appropriate in children less than 2 years of age as their normative maximal values would be below those of the adult or older child; hence most neonates and infants would be classified a priori at a decreased GFR based not on a reduction in GFR from a higher value, but rather failure of maturity of the kidney.

Numerous references exist for fetal, 49 neonatal term, 44, 48 pre-term, 46, 50, 51 infant, child and adolescent GFR values 43, 44 and the reader is strongly encouraged to use such references when comparison to a normative range is required for approximating the reduction in renal clearance of the individual child. It should be noted that across these ages the method of GFR measurement has often varied with the c h a p t e r 1 majority of such measurements in the neonate (term or preterm) or infant being derived from urinary collections and creatinine clearance (CrCl) measurements, whereas the older children and adolescents are often investigated with exogenous markers including inulin, radionuclides, and other markers such as iohexol or iothalamate.

The most comprehensive list of GFR based on the gold standard of inulin clearance and stratified by age for both term and preterm babies and children up to the age of young adults can be found in Schwartz and Furth's review on GFR measurements and estimation in pediatric CKD. 52 imilarly, age relevant normative values should be utilized when interpreting urinary protein (albumin) excretions as well as other important urinary and serum laboratory values. Such values may be found in a number of pediatric nephrology texts. For neonates and infants this includes Waters 53 and for post-neonate to young adults, more comprehensive values can be found in Langlois. 54 2 STAGING OF CKD 1.2.1: We recommend that CKD is classified based on cause, GFR category, and albuminuria category (CGA). (1B)

RATIONALE

This statement is worded in this way because a classification encompassing cause and severity, as expressed by the level of GFR and the level of albuminuria, links to risks of adverse outcomes including mortality and kidney outcomes. These factors will therefore guide management of CKD and this recommended classification is consistent with other classification systems of disease which are based on the general domains of cause, duration and severity which provide a guide to prognosis. We included only kidney measures as factors in the classification of kidney disease, although we acknowledge that factors other than kidney measures, such as level of BP, also affect prognosis in CKD. This recommended staging with inclusion of two additional domains represents a revision of the previous CKD guidelines, which included staging only by level of GFR. Cause of disease is included because of its fundamental importance in predicting the outcome of CKD and choice of cause-specific treatments. With inclusion of cause of kidney disease in the classification, we considered that it was no longer necessary to retain the use of the letter ''T'' to refer to kidney transplant recipients. Albuminuria is included as an additional expression of severity of disease not only because it is a marker of the severity of injury but also because albuminuria itself strongly associates with progression of kidney disease. Numerous studies have identified the adverse prognostic implication of albuminuria irrespective of level of kidney function.

We propose that this classification of CKD by Cause, GFR and Albuminuria, respectively be referred to as CGA staging. It can be used to inform the need for specialist referral, general medical management, and indications for investigation and therapeutic interventions. It will also be a tool for the study of the epidemiology, natural history, and prognosis of CKD.

The principles inherent in this guideline are fully applicable to children.

While large scale trials in children relating cause, GFR and albuminuria or proteinuria are rare, the principles of a multimodal classification in these three spheres should apply to children.

EN_PAPER

KDIGO Board Members

Authors

Keywords

Definition, and classification of CKD 19 Chapter 2: Definition, identification, and prediction of CKD progression 63 Albuminuria, Chronic kidney disease, Classification, Clinical practice guideline, Evidence-based recommendation, GFR, Glomerular filtration rate, KDIGO, Proteinuria, Systematic review

ADULT GFR ESTIMATING EQUATIONS

Abstract

2009 CKD-EPI creatinine equation: 141 Â min(SCr/k, 1) a Â max(SCr/k, 1) À1.209 Â 0.993 Age [ Â 1.018 if female] [ Â 1.159 if black] , where SCr is serum creatinine (in mg/dl), k is 0.7 for females and 0.9 for males, a is À0.329 for females and À0.411 for males, min is the minimum of SCr/k or 1, and max is the maximum of SCr/k or 1.

2012 CKD-EPI creatinine-cystatin C equation: 135 Â min(SCr/k, 1) a Â max(SCr/k, 1) À0.601 Â min(SCysC/0.8, 1) À0.375 Â max(SCysC/ 0.8, 1) À0.711 Â 0.995 Age [ Â 0.969 if female] [ Â 1.08 if black] , where SCr is serum creatinine (in mg/dl), SCysC is serum cystatin C (in mg/l), k is 0.7 for females and 0.9 for males, a is À0.248 for females and À0.207 for males, min(SCr/k, 1) indicates the minimum of SCr/k or 1, and max(SCr/k, 1) indicates the maximum of SCr/k or 1; min(SCysC/0.8, 1) indicates the minimum of SCysC/0.8 or 1 and max(SCysC/ 0.8, 1) indicates the maximum of SCysC/0.8 or 1.

It is our hope that this document will serve several useful purposes. Our primary goal is to improve patient care. We hope to accomplish this, in the short term, by helping clinicians know and better understand the evidence (or lack of evidence) that determines current practice. By providing comprehensive evidence-based recommendations, this guideline will also help define areas where evidence is lacking and research is needed. Helping to define a research agenda is an often neglected, but very important, function of clinical practice guideline development. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system to rate the quality of evidence and the strength of recommendations. In all, there were 12 (17.1%) recommendations in this guideline for which the overall quality of evidence was graded 'A,' whereas 36 (51.4%) were graded 'B,' 17 (24.3%) were graded 'C,' and 5 (7.1%) were graded 'D.' Although there are reasons other than quality of evidence to make a grade 1 or 2 recommendation, in general, there is a correlation between the quality of overall evidence and the strength of the recommendation. Thus, there were 43 (62.3%) recommendations graded '1' and 26 (37.7%) graded '2.' There were 9 (13.0%) recommendations graded '1A,' 23 (33.3%) were '1B,' 10 (14.5%) were '1C,' and 1 (1.4%) was '1D.' There were 2 (2.9%) recommendations graded '2A,' 13 (18.8%) were '2B,' 7 (10.1%) were '2C,' and 4 (5.8%) were '2D.' There were 41 (37.3%) statements that were not graded.

Some argue that recommendations should not be made when evidence is weak. However, clinicians still need to make decisions in their daily practice, and they often ask, ''What do the experts do in this setting?'' We opted to give guidance, rather than remain silent. These recommendations are often rated with a low strength of recommendation and a low quality of evidence, or were not graded. It is important for the users of this guideline to be cognizant of this (see Notice). In every case these recommendations are meant to be a place for clinicians to start, not stop, their inquiries into specific management questions pertinent to the patients they see in daily practice.

We wish to thank the Work Group Co-Chairs, Drs. Adeera Levin and Paul Stevens, along with all of the Work Group members who volunteered countless hours of their time developing this guideline. We also thank the Evidence Review Team members and staff of the National Kidney Foundation who made this project possible. Finally, we owe a special debt of gratitude to the many KDIGO Board members and individuals who volunteered time reviewing the guideline, and making very helpful suggestions.

1.3.2:

In people with CKD, use estimated risk of concurrent complications and future outcomes to guide decisions for testing and treatment for CKD complications. (Not Graded) 1.3.3: In populations with CKD, group GFR and albuminuria categories with similar relative risk for CKD outcomes into risk categories. (Not Graded)

1.4: EVALUATION OF CKD 1.4.1: Evaluation of chronicity 1.4.1.1: In people with GFR o60 ml/min/1.73 m 2 (GFR categories G3a-G5) or markers of kidney damage, review past history and previous measurements to determine duration of kidney disease. (Not Graded) Protein intake 3.1.13: We suggest lowering protein intake to 0.8 g/kg/day in adults with diabetes (2C) or without diabetes (2B) and GFR o30 ml/min/ 1.73 m 2 (GFR categories G4-G5), with appropriate education. 3.1.14: We suggest avoiding high protein intake (41.3 g/kg/day) in adults with CKD at risk of progression. (2C) Glycemic control 3.1.15: We recommend a target hemoglobin A 1c (HbA 1c ) of B7.0% (53 mmol/mol) to prevent or delay progression of the microvascular complications of diabetes, including diabetic kidney disease. (1A) 3.1.16: We recommend not treating to an HbA 1c target of o7.0% (o53 mmol/mol) in patients at risk of hypoglycemia. (1B) 3.1.17: We suggest that target HbA 1c be extended above 7.0% (53 mmol/mol) in individuals with comorbidities or limited life expectancy and risk of hypoglycemia. (2C) 3.1.18: In people with CKD and diabetes, glycemic control should be part of a multifactorial intervention strategy addressing blood pressure control and cardiovascular risk, promoting the use of angiotensin-converting enzyme inhibition or angiotensin receptor blockade, statins, and antiplatelet therapy where clinically indicated. (Not Graded) Salt intake

3.1.19:

We recommend lowering salt intake to o90 mmol (o2 g) per day of sodium (corresponding to 5 g of sodium chloride) in adults, unless contraindicated (see rationale). (1C) 3.1. 19.1: We recommend restriction of sodium intake for children with CKD who have hypertension (systolic and/ or diastolic blood pressure 495 th percentile) or prehypertension (systolic and/or diastolic blood pressure 490 th percentile and o95 th percentile), following the age-based Recommended Daily Intake. (1C) 3.1.19.2: We recommend supplemental free water and sodium supplements for children with CKD and polyuria to avoid chronic intravascular depletion and to promote optimal growth. (1C) Hyperuricemia

3.1.20:

There is insufficient evidence to support or refute the use of agents to lower serum uric acid concentrations in people with CKD and either symptomatic or asymptomatic hyperuricemia in order to delay progression of CKD.

(Not Graded) Lifestyle 3.1.21: We recommend that people with CKD be encouraged to undertake physical activity compatible with cardiovascular health and tolerance (aiming for at least 30 minutes 5 times per week), achieve a healthy weight (BMI 20 to 25, according to country specific demographics), and stop smoking. (1D)

Additional dietary advice 3.1.22: We recommend that individuals with CKD receive expert dietary advice and information in the context of an education program, tailored to severity of CKD and the need to intervene on salt, phosphate, potassium, and protein intake where indicated. (1B)

3.2: COMPLICATIONS ASSOCIATED WITH LOSS OF KIDNEY FUNCTION

Definition and identification of anemia in CKD 3.2.1: Diagnose anemia in adults and children 415 years with CKD when the Hb concentration is o13.0 g/dl (o130 g/l) in males and o12.0 g/dl (o120 g/l) in females. (Not Graded) 3.2.2: Diagnose anemia in children with CKD if Hb concentration is o11.0 g/dl (o110 g/l) in children 0.5-5 years, o11.5 g/dl (115 g/l) in children 5-12 years, and o12.0 g/dl (120 g/l) in children 12-15 years. (Not Graded)

Evaluation of anemia in people with CKD

3.2.3:

To identify anemia in people with CKD measure Hb concentration (Not Graded):

K when clinically indicated in people with GFR Z60 ml/min/1.73 m 2 (GFR categories G1-G2); K at least annually in people with GFR 30-59 ml/min/1.73 m 2 (GFR categories G3a-G3b); K at least twice per year in people with GFRo30 ml/min/1.73 m 2 (GFR categories G4-G5). We recommend measuring serum levels of calcium, phosphate, PTH, and alkaline phosphatase activity at least once in adults with GFR o45 ml/min/1.73 m 2 (GFR categories G3b-G5) in order to determine baseline values and inform prediction equations if used. (1C) 3.3.2: We suggest not to perform bone mineral density testing routinely in those with eGFR o45 ml/min/1.73 m 2 (GFR categories G3b-G5), as information may be misleading or unhelpful. (2B) 3.3.3: In people with GFR o45 ml/min/1.73 m 2 (GFR categories G3b-G5), we suggest maintaining serum phosphate concentrations in the normal range according to local laboratory reference values. (2C) 3.3.4: In people with GFR o45 ml/min/1.73 m 2 (GFR categories G3b-G5) the optimal PTH level is not known.

We suggest that people with levels of intact PTH above the upper normal limit of the assay are first evaluated for hyperphosphatemia, hypocalcemia, and vitamin D deficiency. (2C)

Vitamin D supplementation and bisphosphonates in people with CKD 3.3.5: We suggest not to routinely prescribe vitamin D supplements or vitamin D analogs, in the absence of suspected or documented deficiency, to suppress elevated PTH concentrations in people with CKD not on dialysis. (2B) 3.3.6: We suggest not to prescribe bisphosphonate treatment in people with GFR o30 ml/min/1.73 m 2 (GFR categories G4-G5) without a strong clinical rationale. (2B)

3.4: ACIDOSIS 3.4.1: We suggest that in people with CKD and serum bicarbonate concentrations o22 mmol/l treatment with oral bicarbonate supplementation be given to maintain serum bicarbonate within the normal range, unless contraindicated. (2B)

Chapter 4: Other complications of CKD: CVD, medication dosage, patient safety, infections, hospitalizations, and caveats for investigating complications of CKD 4.1:CKD AND CVD 4.1.1: We recommend that all people with CKD be considered at increased risk for cardiovascular disease. (1A) 4.1.2: We recommend that the level of care for ischemic heart disease offered to people with CKD should not be prejudiced by their CKD. (1A) 4.1.3: We suggest that adults with CKD at risk for atherosclerotic events be offered treatment with antiplatelet agents unless there is an increased bleeding risk that needs to be balanced against the possible cardiovascular benefits. (2B) 4.1.4: We suggest that the level of care for heart failure offered to people with CKD should be the same as is offered to those without CKD. We suggest that dialysis be initiated when one or more of the following are present: symptoms or signs attributable to kidney failure (serositis, acid-base or electrolyte abnormalities, pruritus); inability to control volume status or blood pressure; a progressive deterioration in nutritional status refractory to dietary intervention; or cognitive impairment. This often but not invariably occurs in the GFR range between 5 and 10 ml/min/1.73 m 2 . (2B) 5.3.2: Living donor preemptive renal transplantation in adults should be considered when the GFR is o20 ml/min/ 1.73 m 2 , and there is evidence of progressive and irreversible CKD over the preceding 6-12 months. (Not Graded)

5.4: STRUCTURE AND PROCESS OF COMPREHENSIVE CONSERVATIVE MANAGEMENT

5.4.1: Conservative management should be an option in people who choose not to pursue RRT and this should be supported by a comprehensive management program. (Not Graded) 5.4.2: All CKD programs and care providers should be able to deliver advance care planning for people with a recognized need for end-of-life care, including those people undergoing conservative kidney care. (Not Graded) 5.4.3: Coordinated end-of-life care should be available to people and families through either primary care or specialist care as local circumstances dictate. (Not Graded) 5.4.4: The comprehensive conservative management program should include protocols for symptom and pain management, psychological care, spiritual care, and culturally sensitive care for the dying patient and their family (whether at home, in a hospice or a hospital setting), followed by the provision of culturally appropriate bereavement support. (Not Graded) Referral decision making by GFR and albuminuria. *Referring clinicians may wish to discuss with their nephrology service depending on local arrangements regarding monitoring or referring.

Introduction: The case for updating and context

Kidney International Supplements (2013) 3, 15-18; doi:10.1038/kisup.2012. 63 Justification for updating the guideline for CKD Definition, Evaluation, Classification, and Stratification from an international perspective In 2002, the US-based Kidney Disease Outcomes Quality Initiative (KDOQI) group published a guideline on definition, classification and evaluation of chronic kidney disease (CKD). The guideline proposed uniform definitions of CKD together with a staging system 1 and described issues related to measurement of kidney function that had not previously been identified by the clinical community. This publication revolutionized the concept and management of CKD, generating substantial research and controversy, stimulating discussion, and influencing public policy and laboratory practice. The research generated has led to new insights which require contextualizing in the current era, providing the evidence drivers for updating guidance for defining, diagnosing, staging and managing CKD, and promoting improved care of those with early CKD. Successive international controversies conferences, under the direction of Kidney Disease: Improving Global Outcomes (KDIGO), have shaped the scope of this international update through: 1. Facilitating global implementation of the definition and classification of CKD, identifying areas of uncertainty, and developing a collaborative research agenda to improve the evidence base and facilitate implementation (November 2004). 2. Evaluating the definition and classification of CKD from a global public health perspective (October 2006).

3. Reviewing the definition and classification of CKD

based on data on patient prognosis derived from a unique research collaboration on prognosis (October 2009).

Given the international interest in understanding and improving the outcomes of people living with kidney disease and the tremendous amount of data generated since 2002, a need was identified to review, revise, and update the original 2002 KDOQI guideline.

There has been a wealth of published data highlighting the risk of adverse consequences and outcomes in people with albumin excretion rate (AER) 430 mg/24 hours and/or glomerular filtration rate (GFR) o60 ml/min/1.73 m 2 (GFR categories G3a-G5), irrespective of the etiology or duration of reduced kidney function. 3] [4] [5] Internationally, the widespread use of albumin-tocreatinine ratio (ACR) and reagent strip urine testing to detect elevated albuminuria together with reporting of estimated GFR (eGFR) has led to easier identification of people with CKD. However elevated albuminuria or reduced GFR alone are not necessarily indicators of need for specialist referral. Clinicians and medical systems are still adjusting to the improved ''identification'' of CKD and guidance about appropriate stratification of risk and modified action plans for different subgroups of individuals regarding further evaluation, referral, or treatment is needed.

The goal of this guideline is to clarify the definition and classification system of CKD, and to develop appropriate guidance as to the management and care of people with CKD. In addition, we present a framework which should foster an extended collaborative research agenda over the next decade and inform guidelines in the future.

Kidney disease is an important problem worldwide

Kidney disease is defined as an abnormality of kidney structure or function with implications for the health of an individual, which can occur abruptly, and either resolve or become chronic. CKD is a general term for heterogeneous disorders affecting kidney structure and function with variable clinical presentation, in part related to cause, severity and the rate of progression. The concept of CKD evolved after the recognition of the contribution of disordered kidney structure and function on the health of individuals across a wide range of severity. 1 The utility of the concept is that recognition of CKD will have implications for the individual and their care. Kidney failure is traditionally considered as the most serious outcome of CKD. Symptoms are usually due to complications of decreased kidney function and when severe, they can be treated only by dialysis or transplantation. Earlier stages of kidney disease are often asymptomatic, are detected during the evaluation of comorbid conditions, and may be reversible. Rapidly progressive diseases may lead to kidney failure within months but most diseases evolve over decades, and some patients do not progress during many years of follow-up.

Figure 1 shows a conceptual model for the development, progression, and complications of CKD. 1, 6 The model includes antecedents associated with increased risk for development of CKD, stages of disease, and complications including death. Risks for development of CKD may be categorized either as susceptibility to kidney disease due to sociodemographic and genetic factors or exposure to factors that can initiate kidney disease. Abnormalities in kidney structure (damage) usually precede abnormalities in function. Outcomes of CKD may be progression, as shown by the horizontal arrows, and complications, as shown by the diagonal arrows, or both.

Although the need for treatment of chronic kidney failure with dialysis and/or kidney transplantation arises in only 1% of people with CKD, it remains the most expensive of chronic diseases and reduces lifespan significantly. The costs of dialysis and transplantation consume disproportionate amounts within the health-care budgets in all jurisdictions (5% of annual budgets consumed by less than 1% of the population). Failure to recognize CKD results in neglect of its consequences and complications, and late referral of people with advanced CKD resulting in worse renal replacement therapy (RRT) outcomes. In addition, there is a growing body of evidence that indicates people with CKD are at increased risk of acute kidney injury (AKI), which is also associated with poor outcomes and may accelerate progression of CKD. Therefore, identification of people at earlier time points in the trajectory of CKD, with appropriate management and earlier referral of those who would benefit from specialist kidney services, should lead to both economic and clinical benefits.

In those countries where access to dialysis and transplantation services may be limited or unavailable, the final consequence of progressive CKD is death. In all locations, irrespective of availability of dialysis and transplantation, early identification of CKD therefore assumes great importance, as delay or prevention of progression has the potential to prolong health and save lives for much lower cost than RRT. Although etiologies vary in frequency or absolute numbers in different countries, the proportion of people with important antecedents to CKD, such as diabetes, is growing alarmingly worldwide in both developed and developing countries.

Complications of CKD affect all organ systems. Kidney failure leads to the commonly recognized symptoms of uremia. Less severe CKD has been recognized as an independent risk factor for cardiovascular disease (CVD) and other common conditions affecting the elderly, such as infection and impairments in physical function and cognition. In addition, CKD is associated with increased risk from adverse effects of drugs, intravascular radiocontrast administration, surgery and other invasive procedures. Altogether, these complications are associated with higher morbidity, mortality and cost. If CKD is detected early, the associated complications and the progression to kidney failure can be delayed or even prevented through appropriate interventions. Regular testing of high-risk groups (i.e., people with diabetes, hypertension, CVD, structural renal tract disease, multisystem diseases with potential kidney involvement such as systemic lupus erythematosus, family history of kidney failure, hereditary kidney disease, the elderly, those receiving potential nephrotoxic drugs or those opportunistically found to have hematuria or proteinuria) can give an early indication of kidney damage, thus permitting the introduction of available interventions at an early stage, and the testing of novel interventions with potential added value.

Factors associated with progression of CKD and with increased cardiovascular risk are overlapping to a large extent. Thus targeting of those risk factors that are modifiable may both reduce CVD in people with CKD and reduce progression of CKD to end-stage renal disease (ESRD). There is strong evidence that blockade of the renin-angiotensinaldosterone system (RAAS) is a blood pressure (BP) lowering strategy which is more effective in reducing risk of kidney and cardiovascular disease in the presence of albuminuria.

The development of guidance for health-care providers will provide opportunities to improve the care of people with kidney disease. We hope that this publication serves to stimulate strategic research initiatives from basic, translational, clinical and health outcome perspectives.

1. The guideline will offer best practice and evidence-based advice on the evaluation and approach to management of CKD. a. The target population for the guideline is all people identified with CKD who are not on RRT (i.e., not on dialysis or have not received a kidney transplant). b. The target population includes adults and children.

The guideline will cover the spectrum of individuals with CKD, from children to the elderly who form important subgroups, underscoring current issues at the extremes of age with respect to the evidence base, especially in relation to implementation and management issues. Where the guideline does not apply to Left-pointing horizontal arrowheads signify that remission is less frequent than progression. Diagonal arrows represent occurrence of complications of CKD, including drug toxicity, endocrine and metabolic complications, cardiovascular disease, and others such as infection, cognitive impairment, and frailty. Complications might also arise from adverse effects of interventions to prevent or treat the disease. CKD, chronic kidney disease; EOL, end-of-life care and/or conservative management; GFR, glomerular filtration rate. Adapted from Levey AS, Stevens LA, Coresh J. 6 Conceptual model of CKD: applications and implications. Am J Kidney Dis. 2009; 53:S4-16 with permission from the National Kidney Foundation; accessed http://download.journals. elsevierhealth.com/pdfs/journals/0272-6386/PIIS02726386080 17186.pdf children, statements to that effect will be made. It is beyond the scope of this guideline to address all issues related to children with CKD, given the heterogeneous nature of this group of individuals who range from newborn to post-adolescents, with specific physiological differences within each of those groups. Specific evidence and rationale will be articulated as appropriate in each section. c. c. The target condition is CKD of any or unknown etiology. Identifying the cause of the CKD is strongly encouraged, both because treatment may need to be adjusted according to etiology and because it influences the prognosis and relative importance of risk factors associated with CKD. A comprehensive list of possible etiologies is not practical and guidance on detailed work-up for specific causes of CKD is beyond the scope of this document (readers will be referred to other pertinent sources). We will describe how knowledge of the etiology of CKD in an individual may be important in prognostication and management. d. The target audience of the guideline includes nephrologists, primary care physicians, non-nephrology specialists (e.g., cardiologists, diabetologists, etc), clinical chemists and other practitioners caring for adults and children with CKD. The guideline is also expected to be suitable for use in public policy and other health-care arenas. e. As a global guideline it is written for use in different health-care settings, but unavoidably its full implementation relies on health-care resources that are not universally available. We recognize this overtly in some of the discussion sections within the guideline. f. f. The target health-care settings include primary, secondary, and tertiary care. 2. The guideline will provide information, advice, and education to support self-management for people with CKD and aid caregivers with the diagnosis and management of CKD. To avoid redundancy and potential for becoming outdated, the reader is asked to refer to existing KDIGO guidance on anemia, metabolic bone disease, BP, AKI, hepatitis C, lipid management, glomerulonephritis (GN) and other pertinent guidelines. 3. The guideline will provide a blueprint for an approach to CKD care in an international context. While the guideline will be sensitive to issues related to ethnicity and also geographical considerations, it is expected that subsequent regional adaptation will be required for specific healthcare settings or contexts. 4. Research recommendations in general are described to inform a framework for ongoing research agendas in the international community. We have attempted to identify important study questions in need of answers. Through identification of gaps in knowledge, the reader will be better able to define methodologies, definitions of populations, and outcome measures of relevance to study designs in the future.

Topics that will not be covered

This document is not intended to provide enough detail to replace training and education in nephrology, nor is it intended to serve as a textbook of medicine or nephrology. Thus, there are some specific topics that will not be covered. Specifically we will not discuss: 1. Evaluation and management of people receiving RRT (management of kidney failure by dialysis or kidney transplantation). 2. Specific approaches to the diagnosis of people with AKI and other acute kidney diseases. This topic has been extensively reviewed in KDIGO Clinical Practice Guideline for Acute Kidney Injury. 7 . Diagnostic work-up or treatment of specific causes of CKD, including GN. 8 4. Management of pregnancy in women with CKD or of pregnant women who develop kidney disease. 5. Detailed management of endocrine and metabolic complications of CKD. These are reviewed extensively by recent KDIGO guidelines on CKD-MBD, 9 management of BP 10 and anemia 11 in CKD. 6. Detailed management of CVD and CVD risk factors in CKD. This is reviewed in a recent KDIGO publication. 12 . Drug dosing in CKD. This topic has been addressed in a recent KDIGO publication. 13 . Details of resource implications and barriers to implementation are beyond the scope of this guideline. By virtue of its being international, the variability in these aspects by country, region, and even jurisdiction is vast. We look to the individual commentaries from around the world to inform those aspects more fully.

Brief overview on methodology

The Work Group included an international group of kidney specialists, primary care physicians, diabetologists, epidemiologists, clinical chemists, administrators, and a professional Evidence Review Team (ERT) who provided support and guidance to the group. Details of the methods used by the ERT are described in Methods for Guideline Development, along with the systematic searches for areas identified by Work Group members and performed by the ERT. The recommendations and statements created herein will serve to direct both care and research in the next decade. Importantly, we expect the renewed classification system and risk stratification concepts to direct research and enrollment into trials which address test therapies to improve patient outcomes.

Statement grading and wording. The methods for formulating recommendations were based on modified Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system, and have used the words 'recommend' when the balance of evidence would support the notion that the majority of patients would benefit from the implementation of this recommendation. The words 'suggest' are used when the balance of evidence would support the notion that some patients would benefit from the implementation of the recommendation, but that individual patient, physician and health-care system considerations would be necessary to adopt the practice. There are also ungraded statements many of which are often key practice points or educational issues (Table 1 ). The Work Group had struggled whether to organize them differently or move them to the rationale section. Ultimately they remain here in the guideline statement format so that they are not overlooked by those wishing to understand the condition better.

A significant proportion of statements in this guideline are ungraded because the grading system is most appropriate for statements of intervention. The international system, GRADE, allows for such statements which guide thoughts and attitude, and not specific actions. In the descriptive statements identifying, classifying, and defining the condition of CKD, grading is not possible. Since few studies have compared different methods of evaluation or care models, those statements too are difficult to grade. Thus, grading of specific statements is reserved for interventions or alternative diagnostic test strategies for which there is a substantial body of evidence.

Consideration of health benefits, side effects, and risks.

These have been considered when formulating the recommendations but given the paucity of data in many of the areas reviewed, this has been less consistent than the Work Group would have liked. We see this as an area of research and future study that will inform future updates.

Review process. As with all KDIGO guidelines a two step process was used. This included a review by the Board of Directors, with feedback to the Work Group Chairs followed by revisions to the document. The public review, consisting of interested stakeholders from international communities, organizations and individuals, was then undertaken. The draft document was sent to a total of 2320 external reviewers, with 293 responses received and tabulated. The feedback was carefully reviewed and where appropriate, suggested changes were incorporated into the final document. In the interest of transparency, the Work Group prepared individual responses to each reviewer comment and these will be posted on the KDIGO website.

Planned update. At the current time there is no official plan to update the guideline in its entirety. Given the breadth and depth of the current undertaking and with knowledge of new studies and applications of some of these recommendations, the Work Group recommends that individual sections of this guideline be updated every 3-5 years as new evidence becomes available. We believe that this will be more practical for the readership. Most patients should receive the recommended course of action.

The recommendation can be evaluated as a candidate for developing a policy or a performance measure.

Level 2 ''We suggest''

The majority of people in your situation would want the recommended course of action, but many would not.

Different choices will be appropriate for different patients. Each patient needs help to arrive at a management decision consistent with her or his values and preferences.

The recommendation is likely to require substantial debate and involvement of stakeholders before policy can be determined.

*The additional category ''Not Graded'' was used, typically, to provide guidance based on common sense or where the topic does not allow adequate application of evidence.

The most common examples include recommendations regarding monitoring intervals, counseling, and referral to other clinical specialists. The ungraded recommendations are generally written as simple declarative statements, but are not meant to be interpreted as being stronger recommendations than Level 1 or 2 recommendations.

Chapter 1: Definition and classification of CKD Kidney International Supplements (2013) 3, 19-62; doi:10.1038/kisup.2012.64

1.1: DEFINITION OF CKD 1.1.1: CKD is defined as abnormalities of kidney structure or function, present for 43 months, with implications for health (Table 2 ). (Not Graded)

The definition of CKD remains intact, but we have clarified the classification and risk stratification as indicated below.

The addition of 'with implications for health' is intended to reflect the notion that a variety of abnormalities of kidney structure or function may exist, but not all have implications for health of individuals, and therefore need to be contextualized. Kidney damage refers to a broad range of abnormalities observed during clinical assessment, which may be insensitive and non-specific for the cause of disease but may precede reduction in kidney function (Table 2 ). Excretory, endocrine and metabolic functions decline together in most chronic kidney diseases. GFR is generally accepted as the best overall index of kidney function. We refer to a GFR o60 ml/min/ 1.73 m 2 as decreased GFR (Table 2 ) and a GFR o15 ml/min/ 1.73 m 2 as kidney failure. AKI may occur in patients with CKD and hasten the progression to kidney failure. 14 6] [17] [18] Complications may occur at any stage, often leading to death without progression to kidney failure. Complications may also arise from adverse effects of interventions to prevent or treat the disease and associated comorbidity.

To date the only large scale trial utilizing a validated exogenously measured GFR (iohexol) and urinary protein excretion in a well-described cohort of children with renal disease is the Chronic Kidney Disease in Children (CKiD) trial. 55 They have enrolled over 600 children aged 1-16 years and have described GFR and urinary proteinuria related outcomes in the areas of neurodevelopment, cognition, behavior, cardiovascular health and risk, and somatic growth. They have also collected samples for ongoing and future genetic study. While these data are sparse in relation to overall adult numbers, this represents one of the largest pediatric nephrology trials. The use of true measured GFR, the quality and completeness of the data, and the long term longitudinal follow-up will form the basis for the best evidence-based outcomes in children with CKD for the foreseeable future. A recent review article by Copelovitch et al. 56 summarizes the major findings of the trial up to the present time.

1.2.2: Assign cause of CKD based on presence or absence of systemic disease and the location within the kidney of observed or presumed pathologic-anatomic findings. (Not Graded)

This statement has been included so as to ensure that clinicians are alerted to the fact that CKD is not a diagnosis in and of itself, and that the assignment of cause is important for prognostication and treatment. The cause of CKD has been traditionally assigned based on presence or absence of underlying systemic diseases and location of known or presumed pathologicanatomic abnormalities. The distinction between systemic diseases affecting the kidney and primary kidney diseases is based on the origin and locus of the disease process. In primary kidney disease the process arises and is confined to the kidney whereas in systemic diseases the kidney is only one victim of a specific process, for example diabetes mellitus. Certain genetic diseases cross this boundary by affecting different tissues, e.g., adult polycystic kidney disease. The location of pathologic-anatomic findings is based on the magnitude of proteinuria, findings from the urine sediment examination, imaging, and renal pathology. Table 4 represents an example of a classification of causes of kidney diseases based on these two domains.

There is wide geographic variation in the cause of kidney disease. In developed countries, hypertension and diabetes are the most frequent causes of CKD, especially in the elderly. In populations with a high prevalence of diabetes and hypertension, it can be difficult to distinguish CKD due to hypertension and diabetes from CKD due to other disorders. In other countries, other causes of CKD may be as frequent as hypertension and diabetes (e.g., glomerular disease in East Asia) or coexist with them. Specialized diagnostic testing, such as kidney biopsy or invasive imaging studies are performed only when it is essential to confirm some diagnoses and the benefits justify the risks and cost. It is anticipated that cause of disease will not be known with certainty for many patients with CKD but can be either inferred or not known.

1.2.3: Assign GFR categories as follows [Table 5] (Not

Graded):

The purpose of this statement is to ensure clarity in communication. The terms associated with each of the GFR categories are descriptors which need to be taken in the context of the individual and are all references to normal young adults. Note that mildly decreased kidney function (G2) in the absence of other markers, does not constitute CKD. The associations of lower categories of GFR and risks of metabolic and endocrine complications formed the basis of the previous stratification into 5 stages. This current classification further acknowledges the importance of dividing Stage 3 based on data supporting different outcomes and risk profiles into categories G3a and G3b (Figure 5 ). A number of other concurrent complications are associated with decreased categories of GFR including infection, impaired cognitive and physical function, and threats to patient safety. 57 igures 6 and 7 detail the RRs of decreased eGFR and increasing ACR with future complications, including mortality and kidney outcomes. 30 Even for the group with the lowest value of albuminuria, the increased RR for all outcomes is significant for eGFRs below 60 ml/min/1.73 m 2 in the continuous analysis and in the range of 45-59 ml/min/ 1.73 m 2 for the categorical analysis.

In children o2 years of age with CKD, the GFR categories as per the adult in Table 5 do not apply; these children should be categorized as having normal, moderately reduced, or severely reduced age-adjusted GFR.

No currently agreed upon set of international normative values or categories exist for GFR in children under the age of 1-2 years. However, the international pediatric nephrology community has embraced the adult CKD staging system as per the 2002 KDOQI guidelines in children over the age of 2 years, as suggested by Hogg et al. 43 As indicated in Pediatric Considerations for Guideline 1.1, the normative GFR values for children less than 2 years vary quite widely by both age and method of measurement. More importantly these values are expected to increase in a nonlinear fashion over the first 2 years of life with significant changes seen in the first few months post-birth and no current evidence of presence of comorbid conditions at any given level of measured or estimated GFR in this population. As such, specific categorization of G1-5 as suggested in this Recommendation would seem not be of value, and might be misleading if applied to a child less than 2 years of age.

With this in mind, it is suggested that based on the chosen method of GFR measurement or comparison for the individual (i.e., CrCl, radioactive or cold exogenous serum markers, or estimating formula), that one should attempt to classify the child under the age of 2 years as having normal, moderate or severe reductions in GFR based on the normative range and standard deviations (SDs) for the method. No evidence exists for this recommendation but recognition that values of GFR more than 1 SD below the mean would seem likely to raise concern of the clinician and foster the need for closer monitoring. For drug dosing adjustments it is suggested that those children with GFRs below the mean by 41 but o2 SD be classified as having a moderate reduction in GFR whereas those more than 2 SD below the mean for the method be classified as having a severe reduction in GFR.

1.2.4: Assign albuminuria* categories as follows [Table 6]

(Not Graded): *note that where albuminuria measurement is not available, urine reagent strip results can be substituted (Table 7 )

The purpose of this statement is to ensure communication and to reflect that albuminuria category is an important predictor of outcomes. The association of high levels of proteinuria with signs and symptoms of nephrotic syndrome is well known. The detection and evaluation of lesser quantities of proteinuria have gained additional significance as multiple studies have demonstrated its diagnostic, pathogenic, and prognostic importance. There is a continuous risk associated with albuminuria but the use of a simple categorical approach was selected to simplify the concept for For the detection of diabetic nephropathy some guidelines recommend the use of different ACR thresholds for males and females (425 mg/g [42.5 mg/mmol] and 435 mg/g [43.5 mg/mmol] , respectively) to take into account variations in creatinine excretion. A single threshold is used in North America (30 mg/g or 3.4 mg/mmol). Earlier KDIGO guidance was reluctant to adopt gender-specific thresholds due to greater complexity, uncertainty about assay precision, and effects of race, ethnicity, diet and measures of body size on creatinine and this stance is maintained here. For simplicity, and to reflect the fact that it is an approximation, 3.4 mg/mmol as the current guideline threshold has been rounded to 3.0 mg/mmol.

There is a graded increase in risk for higher albuminuria categories, at all GFR categories, without any clear threshold value. Even for subjects with GFR 460 ml/min/1.73 m 2 , the increased RR is statistically significant for urine ACR Z30 mg/g (Z3 mg/mmol) for mortality and kidney outcomes (Figures 6 and 7 ). The predictive ability of albuminuria at all categories of GFR supports the suggestion to add albuminuria categories to all GFR categories. Since the relationship with albuminuria is continuous, the selection of the number of categories and the cutoff values appears arbitrary. The Work Group has recommended the classification of albuminuria into only 3 categories, based on practical considerations, but recognized that further subdivisions within the category of o30 mg/24 hours (ACRo30 mg/g or o3 mg/mmol) may be useful for risk stratification, and that subdivisions within the category of 4300 mg/ 24 hours (ACR4300 mg/g or 430 mg/mmol) may be useful for diagnosis and management. Specifically there is a recognition that nephrotic range proteinuria (AER42200 mg/24 hours [ACR42200 mg/g;4220 mg/ mmol]; PER43000 mg/24 hours [43000 mg/g;4300 mg/ mmol] ) confers unique additional risks and is usually associated with specific conditions (such as GN). As these are relatively rare in general practices, the simplicity of the AER categorization was preferred. Table 7 shows the approximate relationships of categories of AER to other measures of albuminuria and proteinuria.

Data from around the world suggest that CKD prevalence is between 10-16% but information concerning population prevalence by category of GFR and ACR is scant. Figure 8 shows the proportion of adults in the US by categories of GFR and albuminuria. 19 While CKD is common, few individuals have severely reduced GFR or kidney failure or severely increased albuminuria. The classification of kidney disease by cause, category of GFR and category of albuminuria does not conform to the International Classification of Diseases (ICD) maintained by the World Health Organization (WHO). Currently the WHO is developing an update (ICD 11). It will be important to communicate and coordinate efforts with the kidney disease subgroup for ICD 11. However, the proposed current classification does address the need in clinical practice to acknowledge the multiple dimensions and variables by which individual patients are assessed. Table 8 gives examples of the use of CGA nomenclature.

Definition of GFR categories have been deliberately based upon the concept of ''true'' GFR, whereas clinical practice and research has predominantly used creatinine-based estimates of GFR. The belief of the Work Group is that the non-GFR determinants of creatinine and the imprecision of creatinine-based GFR estimates have resulted in the absence of strong dose-dependent association of eGFR with clinical outcomes in the GFR range of 460 ml/min/1.73 m 2 . The Work Group felt confident that GFR levels of Z90 ml/min/ 1.73 m 2 portend better prognosis than GFR levels 60-89 ml/ min/1.73 m 2 , if they could be estimated accurately. Therefore, the GFR categories include separate G1 (Z90 ml/min/ 1.73 m 2 ) and G2 (60-89 ml/min/1.73 m 2 ) designations despite limited data from creatinine-based estimates that prognosis differs between these two categories. It is also an acknowledgement that the degree of precision of some of our measurements may not be able to differentiate between these 2 categories reliably. As described later, studies that have used cystatin C have found gradients in prognosis at eGFR levels above 60 ml/min/1.73 m 2 , which supports the belief of the committee that separating these 2 GFR categories is appropriate for CKD classification.

Albuminuria categories are ''wide'' with respect to risk, with significant gradients within each category. The decision to propose only 3 categories is based on the perceived need for simplification in clinical practice. In specialized clinical nephrology centers, A3 (4300 mg/g or 430 mg/mmol) is often more precisely assessed and divided into additional categories. For example, nephrotic range proteinuria is defined as PER43500 mg/24 hours or PCR (proteinto-creatinine ratio) 43500 mg/g [4350 mg/mmol] which is approximately equivalent to AER42200 mg/24 hours or ACR42200 mg/g [ Note that the term 'microalbuminuria' is not used and is discouraged in this classification system. This will require a formal education program and review of existing guidelines in other disciplines so that consistency of terminology and 19 Albuminuria is determined by one measurement of ACR and persistence is estimated as described elsewhere. 59 Values in cells do not total to values in margins because of rounding. Category of very high albuminuria includes nephrotic range. Green, low risk (if no other markers of kidney disease, no CKD); Yellow, moderately increased risk; Orange, high risk; Red, very high risk. ACR, albumin-to-creatinine ratio; CKD, chronic kidney disease; CKD-EPI, CKD Epidemiology Collaboration; GFR, glomerular filtration rate; NHANES, National Health and Nutrition Examination Survey. Modified with permission from Macmillan Publishers Ltd: Kidney International. Levey AS, de Jong PE, Coresh J, et al. 30 The definition, classification, and prognosis of chronic kidney disease: a KDIGO controversies conference report. Kidney Int 2011; 80: 17-28; accessed http://www.nature.com/ki/journal/v80/n1/full/ki2010483a.html c h a p t e r 1 understanding of the changes are universal (see Recommendation 1.4.4.2.1).

This statement would need to be altered for application in pediatric practice in the following way. In children with CKD any expression of abnormal urinary protein excretion, irrespective of the marker: K must account for variation in that measurement as seen across age, sex, puberty and or body size (height, weight, body mass index [BMI]).

K should account for the possibility of tubular versus glomerular proteinuria dominance dependent on the underlying disease.

K may utilize proteinuria in place of albuminuria.

There is no set standard encompassing all children with respect to the normal range of urinary protein (or albumin) excretion. ] [62] [63] In general, neonates and young infants/ children are both expected and allowed to have higher urinary losses of both glomerular and tubular proteinuria due to lack of maturation in the proximal tubular reabsorption of proteins. The rough equivalences for ACR and PCR quoted in the pediatric literature are similar, but not identical to those quoted in the adult literature. Normal ranges vary but at least one reference suggests as much as 6-8 mg/m 2 /hr or 4240 mg/m 2 /day of proteinuria as being acceptable at o6 months of age; 64 normal ranges for urinary albumin losses are not known at this age.

The normal range of protein excretion for children 6-24 months of age in a 24-hour urine collection is quoted as being o4 mg/m 2 /hr (o150 mg/m 2 /day), whereas the first morning spot urine protein sample is said to be normal at levels of o500 mg/g creatinine (o50 mg/mmol). In children older than 24 months these values are o4 mg/m 2 /hr (o150 mg/m 2 /day) for the 24-hour collection and PCR o200 mg/g creatinine (o20 mg/mmol) in the first morning urine sample, or a first morning urine ACR o30 mg/g (o3 mg/mmol). 43, 65 t all ages, total urinary protein excretion 440 mg/m 2 /hr (43 grams/1.73 m 2 /day) is considered to represent 'nephrotic range' loss of protein, with intermediate values, i.e., 4-40 mg/m 2 /hr or its equivalent representing abnormal but 'non-nephrotic' losses. 43, 65 hildren older than 24 months of age are expected to achieve normal ('adult') urinary protein values with the caveat of an exaggerated postural loss of glomerular proteins (albumin) as can commonly be seen in the 2-5% of the adolescent population (i.e., orthostatic proteinuria). 62 ased on National Health and Nutrition Examination Survey III (NHANES III) data from just under 6000 healthy 6-19 year old children using either immunonephelometry or radioimmunoassay, the definition of urinary albumin excretion was determined to be 30-300 mg/24 h collection; 20-200 mg/min in an overnight collection and 30-300 mg/g creatinine (3-30 mg/mmol) in a first morning urine sample. 66 f note, to date the majority of studies that have examined the effects of urinary protein losses or therapeutic interventions have concentrated on so-called total protein excretion or random or first morning PCRs. The utility of measuring the albumin only fraction, and in particular quantitating this at the lower level of detection, i.e., o30 mg/g (o3 mg/mmol) creatinine, is only now being investigated in more detail in large pediatric studies. As such it should be recognized that in children the quantification of total protein, as compared to the albumin only fraction, may be the preferred method for assigning risk as it relates to the presence of urinary protein loss. In summary, for children older than 2 years of age the assignment of 'proteinuria' categories can be used as per the adult guidelines with the understanding that modification to the upper limit of expected values may be necessary in consideration of the factors outlined above. Although there is a preference for reporting albumin values, currently many clinicians still categorize these children based on total protein and in the child o2 years of age or the adolescent with demonstrable orthostatic proteinuria, the current albuminuria categories are unlikely to apply.

1.3: PREDICTING PROGNOSIS OF CKD

1.3.1: In predicting risk for outcome of CKD, identify the following variables: 1) cause of CKD; 2) GFR category; 3) albuminuria category; 4) other risk factors and comorbid conditions. (Not Graded) 1.3.2: In people with CKD, use estimated risk of concurrent complications and future outcomes to guide decisions for testing and treatment for CKD complications (Figure 9 ). (Not Graded) 1.3.3: In populations with CKD, group GFR and albuminuria categories with similar relative risk for CKD outcomes into risk categories (Figure 9 ). (Not Graded)

These statements are worded in this way because for all CKD complications, prognosis will vary depending on: 1) cause; 2) GFR; 3) degree of albuminuria; and 4) other comorbid conditions. The relative strength of each of these factors will vary for each complication or outcome of interest. Risk for kidney disease end points, such as kidney failure and AKI, is predominately driven by an individual patient's clinical diagnosis, GFR, and the degree of albuminuria or other markers of kidney damage and injury. For CVD, risk will be determined by history of CVD and traditional and nontraditional CVD risk factors. For other conditions, the risk will be determined by risk factors specific for those conditions. For all conditions, the cause of CKD, GFR category, and albuminuria category will still have important influence as ''risk multipliers,'' but will have smaller overall influence on disease prediction than risk factors specific for the condition. All these conditions have an impact on life expectancy and quality of life (QOL) and contribute substantially to predicting the prognosis of CKD. CKD is associated with numerous complications directly or indirectly related to the cause of CKD, decreased GFR, or albuminuria (Table 9 ). The risk associations of GFR and albuminuria categories appear to be largely independent of one another. Therefore, neither the category of GFR nor the category of albuminuria alone can fully capture prognosis for a patient with CKD. The magnitude and gradients of risk across categories of GFR and albuminuria will likely differ for each specific adverse event. This heterogeneity across the GFR and ACR grids in RRs for different outcomes makes it impractical to have a simple hierarchical staging of prognosis across all cells. Thus, the staging using CGA should be descriptive, but encompassing the ordered categories of GFR and ACR (Figure 9 ). The CGA staging system proposed in this guideline provides a framework for future recommendations on CKD clinical management. At present, much of the evidence on clinical decision making in CKD is based solely on GFR. This recommendation serves to highlight the multidimensional c h a p t e r 1 aspect of CKD so as to ensure appropriate consideration of the complexity of the condition.

Evidence Base

The evidence base from which these statements are derived includes large observational cohort studies from diverse populations. For some outcomes, including mortality, CVD, and kidney disease progression, metaanalyses have summarized the risk associations. For outcomes that occur predominately in older adults (e.g., dementia, fracture), the evidence is largely limited to cohorts of older people. Extensive work by the CKD Prognosis Consortium has defined the RRs across GFR and albuminuria categories for several important outcomes, including all-cause mortality, CVD, and kidney failure (Figures 6 and 7 ). Risk increases incrementally in both directions -down the GFR categories and across the albuminuria categories. Levels of risk can be identified and grouped into categories, but they may differ somewhat for each outcome. Additional research is needed to map these GFR and albuminuria categories and cause of kidney disease to other important outcomes of CKD (Table 9 ).

International Relevance

The above statements appear to be robust when applied in North America, Europe and Asia. 30 Thus, it appears for all methods used to determine GFR and to detect albuminuria, the use of the 3 parameters (cause, category of GFR and category of albuminuria) influences prognosis irrespective of ethnicity or country of origin.

Providers must incorporate cause of kidney disease, GFR category and albuminuria category in order to better develop an accurate assessment of an individual's prognosis related to CKD. Many providers who are not nephrologists will need guidance in the local methods for requesting and interpreting a urine albumin assessment and an eGFR. Use of risk scores which are being developed and refined is advised.

Public policy and estimates of total burden of illness in a community need to take into account the incidence and prevalence of specific conditions (such as diabetes and congestive heart failure). In addition, knowledge of distribution of levels of eGFR and ACR may be valuable for resource planning. Community or health-system based interventions to reduce the incidence of kidney failure in populations should be targeted and prioritized based on these 3 criteria.

The primary impact on clinical practice will relate to kidney-specific complications of CKD and referral patterns to help prevent and manage them. Decisions related to screening and monitoring CKD disorders will be informed and guided by the CGA system. At present, this evidence for issues such as management of anemia, CKD bone and mineral disorders, and acid-base disorders has not been organized and presented in this way.

Decisions on screening and referral strategies have major impact on the costs and quality of health-care. The value of 30 The definition, classification, and prognosis of chronic kidney disease: a KDIGO controversies conference report. Kidney Int 2011; 80: 17-28; accessed http://www.nature.com/ki/journal/v80/n1/full/ki2010483a.html this revised system of classification is that it will allow the evaluation of different referral patterns and the impact of treatment strategies in those with diverse CGA assignment. In this way, we will develop additional evidence which will inform practice patterns. These will necessarily be developed locally and reflect the values and economic realities of each health-care system.

Areas of Controversy, Confusion, or Non-consensus and Clarification of Issues and Key points Current clinical practice has not overtly incorporated these 3 variables into all decision making activities. The utility of the system will need to be vetted by those referring and those to whom patients are referred. The overt description of the 3 dimensions of diagnosis and staging of kidney disease which include the cause, the category of GFR and the category of albuminuria, should help to inform referral and treatment patterns of large groups of individuals. Risk calculators for specific events are under development.

K The CGA classification system will be useful for quantifying risk for specific outcomes of CKD but its utility has not been fully assessed in clinical practice and research studies.

K Additional evidence is required before decisions on screening, monitoring, and referral patterns can be fully informed.

For Recommendation 1.3.1 the rationale and principles behind this statement would apply to pediatrics though the data are not available. Unlike in adults, the knowledge of risk of progression or outcomes of CKD is less robust in children, with the majority of such information gleaned from either registry datasets or longitudinal trials. In a 2008 report of a select group of patients enrolled by various North American pediatric nephrology centers in the North American Pediatric Renal Trials and Collaborative Studies (NAPRTCS) registry, 46% of nearly 7100 cases had reached a final 'end point' with 86% progressing to ESRD over their time in the registry. 69 Data from the prospective registry and population-based Italian Pediatric Registry of Chronic Renal Failure (ItalKid) study demonstrated a risk of progression to ESRD of B68% by age 20 years. 70 ause of CKD. Specific information related to rate of progression for all pediatric causes of CKD is not easily available. However data from the prospective longitudinal CKiD trial has demonstrated a more rapid decline in renal function in children whose underlying cause of CKD is classified as glomerular with an annualized rate of change in iohexol GFR of À10.5% as compared to those with a non-glomerular cause in whom the annualized rate of change is only À3.9%. 71 In terms of absolute rates of change in measured iohexol GFR this translated, in a separate analysis from the same dataset, into a median change of GFR of À4.3 ml/min/1.73 m 2 versus À1.5 ml/min/ 1.73 m 2 in the glomerular versus non-glomerular groups, respectively. 72 This paper also provides the only current individual disease-specific estimate of annual decline in a pediatric population. Table 10 illustrates that the median values for annualized change in GFR for various diagnosis categories.

Similarly, a randomized controlled trial (RCT) from Europe 73 examining the effects of diet on rate of progression demonstrated a statistically significant difference in CrCl between their glomerular and non-glomerular cohorts at 2 years of follow-up; with the mean decline [SD] in the glomerular group being À10.7 [11.3] versus À8.4 [13.5] ml/ min/1.73 m 2 in the non-glomerular patients (P ¼ 0.048).

GFR category. It is also well recognized that there is an inverse relationship between the rates of progression of kidney disease to the level of kidney function present at that presentation with more rapid decline seen in patients with lower initial levels of GFR. Staples et al. 74 in their retrospective review of the NAPRTCS CKD database involving nearly 4200 children registered with GFR categories G2-G4 (GFR 15-89 ml/min/1.73m 2 ) demonstrated significantly higher rates of progression, defined by progression to GFR category G5 (GFR o15 ml/min/1.73m 2 ) or initiation of dialysis or transplant, for children in GFR categories G3a-G4 (GFR 15-59 ml/min/1.73m 2 ) as compared to those with CKD and GFR category G2 (GFR 60-89 ml/min/1.73m 2 ) at time of enrollment: hazard ratio (HR) of GFR categories 3a and 3b (GFR 30-59 ml/min/1.73m 2 ) (GFR category 2 (GFR 60-89 ml/min/1.73m 2 ) ¼ 1.00 as referent): 2.00; 95% confidence interval (CI) 1.64-2.42; Po0.0001 and HR of GFR category 4 (GFR 15-29 ml/min/1.73m 2 ): 6.68; 95% CI 5.46-8.18; Po0.0001.

Albuminuria (proteinuria). Several studies have also demonstrated the effect of proteinuria on rate of progression of CKD in children. Using registry data, and in non-glomerular conditions the ItalKids trial 75 demonstrated a significantly slower decline in CrCl in patients with baseline PCRs of o200 mg/g (20 mg/mmol) and 200-900 mg/g (20-90 mg/ mmol) when compared to those patients with a PCR of 4900 mg/g (490 mg/mmol); slope þ 0.16 ± 3.64 and In a prospective multicenter randomized trial of protein intake on rates of progression in children aged 2-18 years of age, Wingen et al. employed the Schwartz equation to estimate CrCl and demonstrated that baseline proteinuria in multivariate analysis was the most important independent predictor of change in CrCl. The authors reported a partial R 2 of 0.259 at 2 years follow-up and similar results were found after the study was extended for a third year. 73 Lifetable analysis in this study also suggested a cutoff value of 50 mg/kg/day of proteinuria as a strong predictor of time to a decline in CrCl410 ml/min/1.73 m 2 and found a risk ratio of 4.01 (95% CI 2.23-7.25; Po0.001).

Finally Wong et al. 76 used cross sectional data from the prospective longitudinal CKiD trial to demonstrate that even after controlling for age, race, BMI, cause of CKD and use of RAAS antagonists they could expect an average decline in measured GFR of 10% for every increase in urinary PCR of 14% (95% CI 10-18%).

Other risk factors and comorbid conditions. Many other risk factors and comorbid conditions have also been associated with greater risk of progression of CKD in adults but only a few of these have been convincingly proven in children due to lack of pediatric prospective trials.

Hypertension is by far the best studied of these risk factors in children, with clear evidence from multiple sources to document the value of aggressive BP control on slowing the rate of progression of CKD. Wingen et al. 73 demonstrated the importance of systolic BP in rate of progression in both univariate and multivariate models. In this study Cox proportional hazards analysis demonstrated a systolic BP 4120 mm Hg was an independent risk for decline in CrCl by 410 ml/min/1.73 m 2 ; risk ratio was 3.1 (95% CI 1.74-5.53; Po0.001).

The most important prospective pediatric BP trial to date, the Effect of Strict Blood Pressure Control and ACE-Inhibition on Progression of Chronic Renal Failure in Pediatric Patients (ESCAPE) study, used ambulatory BP monitoring (ABPM) and a fixed dose of ramipril plus additional antihypertensive agents that do not target the RAAS to assess (as primary outcomes) the time to decline of 50% in GFR or development of ESRD. Their results demonstrated a 35% reduction in the risk of achieving the primary end point in the more intensely treated BP: HR 0.65; 95% CI 0.44-0.94; P ¼ 0.02. Further sub-analysis as reported in the KDIGO BP Guideline 10 demonstrated that kidney survival was 66.1% at 5 year follow-up in patients with systolic BPo90 th percentile for age whereas it was 41% in the patients who did not achieve this level of reduction (P ¼ 0.0002); similar numbers were seen if diastolic BP was the metric considered.

The issue of puberty and its effect on rate of progression has recently been addressed by the ItalKids investigators. 77 hile the methodology of their analysis is less than ideal as they did not determine actual Tanner stages in the majority of their cohort and used estimated rather than measured GFR, they do appear to demonstrate a decrease in kidney survival probability beginning around 10.9 years in girls and 11.6 years in boys with CKD. Of note, the rate of decline in kidney survival, using these age points as 'inflection' or break points, is dramatically increased in both sexes based on their evidence provided in graphical form, although more precise analyses are not possible from the data provided.

As in adults, other factors for consideration and value in monitoring in children with respect to risk of progression include obesity, metabolic acidosis, anemia, calcium-phosphate metabolism, chronic inflammation, diabetes, hyperuricemia, dyslipidemia, and smoking.

The most comprehensive review of many of these factors in children comes from a retrospective study of the NAPRTCS CKD database. Staples et al. 74 demonstrated that in a multivariate analysis of nearly 4200 children registered with CKD and GFR categories G2-G4 (GFR 15-89 ml/min/ 1.73m 2 ), the following factors were significantly associated with the risk of CKD progression (defined by progression to GFR category G5 (GFRo15 ml/min/1.73m 2 ) or initiation of dialysis or transplant): age; primary disease; GFR category; registration year; hypertension; corrected calcium, phosphorus, albumin, and hematocrit; and as proxies, the use of medications for anemia and short stature. The ability of this paper to prove causation or value in treating any of these conditions in hopes of delaying CKD progression is limited by its retrospective nature, and the fact that data were accrued from a voluntary registry.

There is optimism that prospective data from current large pediatric trials such as CKiD 55 and the European Cardiovascular Comorbidity in Children with CKD (4C) trial 78 will lead to a better understanding of how risk factors may be influencing the rate of progression of CKD in children.

For Recommendation 1.3.2 the rationale and principles behind this statement would apply to pediatrics, though the data are not available. Insufficient evidence currently exists with respect to the predictive value of prevalent risk factors to guide future decisions for testing or treatment for CKD complications in an individual child.

It is hoped that well powered, prospective trials with adequate follow-up, such as the CKiD 55 and European 4C 78 trials, will gather sufficient numbers of patients, comorbidities, and outcomes to allow for predictive models to be built in pediatric CKD that incorporate traditional and nontraditional cardiac risk factors including dyslipidemia and hypertension, proteinuria (albuminuria), specific diseaserelated issues (e.g., diabetes, tubulopathy), prematurity, and birth weight.

For Recommendation 1.3.3 the rationale and principles behind this statement would apply to pediatrics, though the data are not available. Current evidence and a paucity of numbers do not allow for the statistically relevant categorization of RR for CKD outcomes based solely on GFR and albuminuria or proteinuria. Again both the CKiD 55 and European 4C 78 trials may be able to address these shortcomings.

1.4: EVALUATION

Once the presence of CKD is proven it is essential to establish a cause for this which will inform specific management and modify risk projections. The diagnosis will be reached by standard clinical method (i.e., history examination) and special investigation, based on knowledge of the common causes of CKD and their manifestations. Not all evaluations are required in all patients, and will be directed by clinical context, and resource availability. For most patients the following evaluations are indicated:

K Reagent strip urinalysis to detect hematuria or pyuria. If positive, use urine microscopy to detect RBC casts or WBC casts.

K Ultrasound to assess kidney structure (i.e., kidney shape, size, symmetry and evidence of obstruction) as clinically indicated.

K Serum and urine electrolytes to assess renal tubular disorders, as clinically indicated.

Many individuals found to have CKD will not have a primary kidney disease but kidney damage caused by diabetes mellitus, vascular disease, and hypertension. The issue for the clinician will be to decide whether the presence of these is a sufficient explanation and if not, to investigate further. The prevalence of other conditions will vary depending on region, age, and other factors.

It is beyond the scope of this guideline to describe how specific diagnoses are reached but non-nephrologists in the first instance should review the family history, medications, symptoms and signs for manifestations of systemic diseases. Urinalysis should be performed, along with imaging of the kidneys if obstruction of the urinary tract or polycystic kidney disease is considered.

For Recommendations 1.4.1.1 and 1.4.2.1, the statements would need to be altered for application in pediatric practice in the following way.

In any child with GFRo60 ml/min/1.73 m 2 (or more than 1 SD below expected for their age and sex) or with markers of kidney damage, a complete review of their past history and previous measurement or estimate of renal function and full consideration of the clinical context, including prenatal history, drug exposures of fetus or mother, genetic conditions, coincident organ abnormalities, physical examination, fetal and post-natal laboratory measures including amniotic fluid, pre-and post-natal imaging and pathologic diagnosis including those of the fetus and placenta should be used to determine the cause(s) of kidney disease.

As noted in Pediatric Considerations for Recommendation 1.1.1, developmental renal abnormalities account for as many as 30-50% of the children with CKD. 42 A careful review of all fetal or maternal exposures, genetic risks factors, and any relevant information on the intrauterine environment during gestation are all relevant to the determination of the presence of CKD either prior to or present immediately at the time of delivery. An infant may be born with CKD, leading to c h a p t e r 1 immediate classification within the CGA framework -up to and including that of dialysis dependency.

1.4.3 Evaluation of GFR

This section describes the various methods by which GFR can be estimated. We describe laboratory techniques that satisfy the requirements for robust result reporting and we compare the accuracy of available equations for the purpose of reporting eGFR using a single equation where applicable. We emphasize equations based on standardized measurements of SCr, but also consider newly developed equations based on standardized measurements of serum cystatin C (SCysC) because they are being introduced into clinical practice. We encourage practitioners to have a clear understanding of the value and limitations of both filtration markers, the importance of standardization of assays for both, and to understand that when an accurate assessment of kidney function is required, direct measurement should be undertaken.

1.4.

RATIONALE

These statements specifically address the need to ensure that estimating equations are put into routine clinical practice, and that clinicians understand the utility of further evaluation with additional methods if required. GFR is measured by the clearance of an exogenous or endogenous filtration marker. 27 All clearance methods are complex so in clinical practice, GFR is estimated from the serum concentration of the endogenous filtration marker creatinine. Cystatin C is an alternative endogenous filtration marker; other filtration markers are also under evaluation. The principles of GFR estimation are discussed in the rationale for recommendations regarding the use of creatinine as a filtration marker but the concepts apply to GFR estimation from all endogenous filtration markers. Specific comments about GFR estimation using cystatin C are presented separately.

For most clinical circumstances, estimating GFR from SCr is appropriate for diagnosis, staging, and tracking the progression of CKD. However, like all diagnostic tests, interpretation is influenced by varying test characteristics in selected clinical circumstances and the prior probability of disease. In particular, an isolated decreased eGFR in otherwise healthy individuals is more likely to be false positive than in individuals with risk factors for kidney disease or markers of kidney damage. Confirmation of decreased eGFR by measurement of an alternative endogenous filtration marker (cystatin C) or a clearance measurement is warranted in specific circumstances when GFR estimates based on SCr are thought to be inaccurate and when decisions depend on more accurate knowledge of GFR, such as confirming a diagnosis of CKD, determining eligibility for kidney donation, or adjusting dosage of toxic drugs that are excreted by the kidneys. 79 The choice of confirmatory test depends on the clinical circumstance and the availability of methods where the patient is treated.

Pediatric Considerations

For Recommendation 1.4.3.1, the statements would need to be altered for application in pediatric practice in the following way. The use of SCr and a recently derived pediatric specific GFR estimating equation, which incorporates a height term, 80 is preferred over the use of SCr alone in the initial assessment of pediatric renal function.

For Recommendation 1.

Estimating GFR from the SCr concentration alone requires implicit judgments that are difficult in routine clinical care, including reciprocal transformation, consideration of the non-GFR determinants, and conversion to the GFR scale. Using GFR estimating equations provides a more direct assessment of GFR than SCr alone. The SCr concentration is influenced by GFR and other physiological processes, collectively termed ''non-GFR determinants,'' including creatinine generation by muscle and dietary intake, tubular creatinine secretion by organic anion transporters, and extrarenal creatinine elimination by the gastrointestinal tract (Figure 10 ).

GFR estimating equations are developed using regression to relate the measured GFR to steady state SCr concentration and a combination of demographic and clinical variables as surrogates of the non-GFR determinants of SCr. By definition, GFR estimates using SCr concentration are more accurate in estimating measured GFR than the SCr concentration alone in the study population in which they were developed. Sources of error in GFR estimation from SCr concentration include nonsteady state conditions, non-GFR determinants of SCr, measurement error at higher GFR, and interferences with the creatinine assays (Table 11 ). GFR estimates are less precise at higher GFR levels than at lower levels.

The clinician should remain aware of caveats for any estimating equation which may influence the accuracy in a given individual patient.

Because of the physiologic and statistical considerations in developing GFR estimating equations, GFR estimates are less precise at higher GFR levels than at lower levels. In principle, equations based on multiple endogenous filtration markers can overcome some of the imprecision of GFR estimates at higher levels, due to cancellation of errors from noncorrelated non-GFR determinants.

This guideline is fully applicable in pediatrics. We recommend that serum creatinine concentration be reported and rounded to the nearest whole number when expressed as standard international units (lmol/l) and rounded to the nearest 100 th of a whole number when expressed as conventional units (mg/dl).

Figure 10 | Determinants of the serum level of endogenous filtration markers. The plasma level (P) of an endogenous filtration marker is determined by its generation (G) from cells and diet, extrarenal elimination (E) by gut and liver, and urinary excretion (UV) by the kidney. Urinary excretion is the sum of filtered load (GFR X P), tubular secretion (TS), and reabsorption (TR). In the steady state, urinary excretion equals generation and extrarenal elimination. By substitution and rearrangement, GFR can be expressed as the ratio of the non-GFR determinants (G, TS, TR, and E) to the plasma level. GFR, glomerular filtration rate. Reprinted with permission of American Society of Nephrology, Measured GFR as a confirmatory test for estimated GFR, Stevens LA, Levey AS. 79 We recommend that eGFR creat should be reported and rounded to the nearest whole number and relative to a body surface area of 1.73 m 2 in adults using the units ml/min/ 1.73 m 2 .

K

We recommend eGFR creat levels less than 60 ml/min/1.73 m 2 should be reported as ''decreased.''

The statement is worded this way to acknowledge that calibration of assays is essential to interpretation of kidney function measures. This recommendation is directed to laboratories with the intent to clarify the details of such calibration and the use of specific equations so as to facilitate international standardization. 81 here are numerous assay methods for creatinine for use in clinical laboratories. Variation in assigned values for SCr concentration among methods is greater at low concentrations, corresponding to high levels of GFR. Variation in assays at low SCr concentrations contributes to imprecision of GFR estimates at high GFR levels.

Currently available assays fall into two broad categories, the alkaline picrate (Jaffe) assay and enzymatic assays. In general, enzymatic assays are less biased compared to a standardized reference material and less susceptible to interferences. All assays are available on a number of platforms.

We recommend that laboratories use assays that are traceable to pure creatinine standards via a valid calibration hierarchy and that are specific and minimally-biased compared with isotope-dilution mass spectrometry (IDMS) reference method results. Results should be traceable to reference materials and methods listed on the Joint Committee for Traceability in Laboratory Medicine (JCTLM) database. Ideally laboratories should move to enzymatic assays for creatinine measurement: as a minimum, the use of traditional kinetic or end point Jaffe assays should cease and be replaced with IDMS aligned Jaffe methods.

Clinical laboratory information systems generally have access to patient age and sex and thus can report eGFR based on SCr age and sex, thus providing the clinician with the test result in units which are recommended for interpretation. Estimated GFR is now reported together with SCr when creatinine is ordered in more than 75% of clinical laboratories in the US. 82 In the UK, 93% of NHS laboratories report eGFR with SCr, 83 as is the case in Australia, Canada, and many European countries.

Selection of a single equation for use, where applicable, would facilitate communication among providers, patients, researchers and public health officials. Criteria for selection should be based on accuracy compared to measured GFR and usefulness in clinical care and public health.

The interpretation of measured and eGFR is based on comparison to normative values, which are adjusted for BSA because of the physiologic matching of GFR to kidney size, which is in turn related to BSA. The value of 1.73 m 2 reflects the average value of BSA of 25-year old men and women in the USA in 1927. 84 While it is known that modern populations may have different normal values for BSA, the 1.73 m 2 value will be maintained for normalization purposes.

Drug dosing should be based on GFR which is not adjusted for BSA. The effect of drug dosing based on GFR adjusted for BSA compared to GFR unadjusted for BSA has not been studied rigorously and more precise recommendations are not available.

Flagging decreased values for eGFR can alert clinicians to the possibility of AKD or CKD, and may indicate the need for additional investigations or treatments, including adjustment of doses of drugs that are excreted by the kidney. However, values for GFR between 60 and 89 ml/min/1.73 m 2 are mildly decreased compared to the usual values in young healthy people. Thus it is important that clinicians appreciate that eGFR values that are not flagged because they are 460 ml/ min/1.73 m 2 are not necessarily normal.

Evidence Base

Numerous equations have been developed to estimate GFR or CrCl in adults. In general, GFR estimating equations using creatinine include age, sex, race, and body size as surrogates for creatinine generation by muscle. For our review of GFR estimating equations, we only considered equations that were developing using assays that were traceable to reference methods and study populations in which SCr concentration was measured using traceable assays (Supplemental Table 1 ). 85 ased on published data, only the Modification of Diet in Renal Disease (MDRD) Study equation, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and modifications of these equations were developed using creatinine assays traceable to the international reference material for creatinine (Table 12 ). 86, 87 The Cockcroft and Gault formula and others were developed before standardization of creatinine assays but cannot be re-expressed for use with standardized creatinine assays (Supplemental Table 2 ).

The MDRD Study equation was developed in 1999 and is currently recommended for eGFR reporting in adults by the National Kidney Disease Education Program (NKDEP) and by the Department of Health in the UK. It uses standardized SCr, age, sex, and race (black versus white and other) to estimate GFR adjusted for BSA (ml/min/1.73 m 2 ). 86, 94 ecause of imprecision at higher GFR, NKDEP recommends that eGFR Z60 ml/min/1.73 m 2 computed using the MDRD Study equation not be reported as a numeric value. For a similar reason, the UK Department of Health recommends not reporting eGFR 490 ml/min/1.73 m 2 using the MDRD Study equation as a numeric value.

The CKD-EPI equation was developed in 2009 and uses the same four variables as the MDRD Study equation. 87 The CKD-EPI equation had less bias than the MDRD Study equation, especially at GFRZ60 ml/min/1.73 m 2 , a small c h a p t e r 1 improvement in precision, and greater accuracy (Figure 11 ).

Most but not all studies from North America, Europe and Australia show that the CKD-EPI equation is more accurate than the MDRD Study equation, especially at higher GFR (Table 13 ), 85 which enables reporting of numeric values across the range of GFR. At this time, large commercial clinical laboratories in the US have changed from using the MDRD Study equation to the CKD-EPI equation for eGFR reporting.

Lesser bias of the CKD-EPI equation compared to the MDRD Study equation reflects higher eGFR throughout most of the range for age and creatinine, especially in younger individuals, women and whites. Higher eGFR results in lower prevalence estimates for CKD in these groups (Figure 12 ), with more accurate risk relationships of lower eGFR and adverse outcomes (Figure 13 ). 107 o account for possible differences in muscle mass and diet according to race, ethnicity and geographic region, the MDRD Study and CKD-EPI equations have been modified for use in other racial and ethnic groups and in other countries. In some, but not all studies, these modifications are associated with increased accuracy (Table 14 ), and should be used in preference to unmodified equations. Where tested, the CKD-EPI equation and its modifications were generally more accurate than the MDRD Study and its modifications. In the absence of specific modifications for race, ethnicity, or regional difference, it is reasonable to use the CKD-EPI equation for GFR estimation. Reliance upon SCr alone is not an appropriate alternative since the uncertainty about the effect of non-GFR determinants affects interpretation of SCr as much as it affects interpretation of eGFR. More widespread testing of GFR estimating equations is necessary to resolve uncertainties about the need for racial, ethnic, and geographic modifications. 108

This recommendation would need to be altered for application in pediatric practice in the following way.

K Creatinine measurements in all infants and children should be derived from methods that minimize confounders and are calibrated against an international standard.

K eGFR creat may only be reported when the height of the child is known by the laboratory.

K If reporting eGFR creat laboratories should utilize the most current and accurate pediatric derived equations based on the demographic and laboratory markers available.

In infants or small children the level of creatinine when measured is often below that of the normal 'bottom range' of the adult assay. As such laboratories measuring creatinine in infants or small children must ensure their lower calibration samples include the lowest end of the expected range of values for the group of interest.

As the majority and the most accurate of the published pediatric eGFR creat formulas require height, standard laboratory reporting of eGFR creat is neither practical nor recommended in children. In a pediatric CKD population, and using the plasma disappearance of iohexol as the gold standard measure of GFR, Schwartz et al. derived a number of novel GFR prediction equations. 80 Their analysis demonstrated the importance of the height/SCr variable in the population as it provided the best correlation with the iohexol GFR (R 2 ¼ 65%). The simplest of such formula, using only height and SCr and a constant of either 41.3 or 0.413 depending on whether height was expressed as meters or centimeters respectively, provided 79% of estimated GFRs within 30% of the iohexol values and 37% of estimated GFRs within 10% of the iohexol values. y Evaluated as the root mean squared error for the regression of estimated GFR on measured GFR.

|| Evaluated as the IQR for the differences between estimated and measured GFR.

z Evaluated as the SD of the differences between estimated and measured GFR. **Converted to raw scale by multiplying percentage of bias by measured GFR. Reprinted with permission from Earley A, Miskulin D, Lamb EJ, et al. 85 Estimating equations for glomerular filtration rate in the era of creatinine standardization: a systematic review. Ann Intern Med 2012; 156 (11): 785-795.

c h a p t e r 1

Any eGFR creat formula used in children will preferably be validated at the appropriate age and level of renal function, and the laboratory methods used locally will be calibrated or comparable to those used in the process of developing the formula being applied. Currently the most robust pediatric eGFR formulas, derived using iohexol disappearance and creatinine measurements which were measured centrally and calibrated and traceable to international standards come from the CKiDs study. 80 he two most common creatinine-based formulas recommended for use in clinical practice include: Updated ''Bedside'' Schwartz equation: eGFR (ml/min/1.73 m 2 ) ¼ 41.3 Â (height/SCr), where height is in meters and SCr is in mg/dl. ''1B'' Equation (include blood urea nitrogen [BUN] not cystatin C): eGFR (ml/min/1.73 m 2 ) ¼ 40.7 Â (height/SCr) 0.64 Â (30/ BUN) 0.202 , where height is in meters, SCr and BUN are in mg/dl.

The additional recommendation for laboratory reporting of SCr is fully applicable in pediatrics.

When the individual clinician has information regarding current and accurate height and applies the appropriate pediatric formula, the recommendation to report an individual child's eGFR creat value of less than 60 ml/min/ 1.73 m 2 as ''decreased,'' would be applicable in children over the age of 2 years.

1.4.3.5: We suggest measuring cystatin C in adults with

eGFR creat 45-59 ml/min/1.73m 2 who do not have markers of kidney damage if confirmation of CKD is required. (2C)

If eGFR cys /eGFR creat-cys is also o60 ml/min/ 1.73 m 2 , the diagnosis of CKD is confirmed.

If eGFR cys /eGFR creat-cys is Z60 ml/min/1.73 m 2 , the diagnosis of CKD is not confirmed.

A major foundation of this guideline is that CKD classification and staging should be influenced primarily by clinical prognosis. As will be reviewed in the sections below, abundant evidence has shown that GFR estimates based on cystatin C are more powerful predictors of clinical outcomes than creatinine-based eGFR. These findings have been strongest for mortality and CVD events, and the prognostic advantage of cystatin C is most apparent among individuals with GFR 445 ml/min/1.73 m 2 . In addition, new findings show that using cystatin C in addition to SCr can lead to improved accuracy of GFR estimation, including CKD classification. In the opinion of the Work Group, these considerations warrant new recommendations for GFR estimation using cystatin C.

Evidence supports the use of cystatin C-based eGFR within the population of persons diagnosed with CKD based on an eGFR creat 45-59 ml/min/1.73 m 2 (G3a) but without albuminuria (A1) or other manifestations of kidney damage. This group represents 3.6% of the US population and 41% of people in the US estimated to have CKD based on eGFR creat and urine ACR alone (Figure 8 ), and there has been substantial controversy over whether or not these persons have CKD. Data described below indicate that use of cystatin C to estimate GFR in this population leads to more accurate estimation of GFR and prediction of risk for future adverse events.

In several studies, eGFR cys has been measured in populations with and without eGFR creat o60 ml/min/ 1.73 m 2 , and participants were separated into those with and without eGFR cys o60 ml/min/1.73 m 2 (Figure 14 ). Those with both eGFR creat and eGFR cys o60 ml/min/1.73 m 2 , about two-thirds of those with eGFR creat o60 ml/min/1.73 m 2 , had markedly elevated risks for death, CVD, and ESRD end points compared with persons with eGFR creat 460 ml/min/1.73 m 2 . The Work Group therefore considers this group to have ''confirmed CKD.'' In contrast, about one-third of those with eGFR creat o60 ml/min/1.73 m 2 had eGFR cys 460 ml/ min/1.73 m 2 and this group were similar in risk for adverse outcomes as persons with eGFR creat 460 ml/min/1.73 m 2 .

New data from CKD-EPI also showed improved accuracy in GFR estimation using both creatinine and cystatin C (eGFR creat-cys ) compared to either marker alone. In the subgroup with eGFR creat 45-59 ml/min/1.73 m 2 , the combined equation correctly reclassified 16.8% of those with eGFR 45-59 ml/min/1.73 m 2 to measured GFR Z60 ml/min/ 1.73 m 2 . 113 he consensus of the Work Group was therefore that the large group of persons with eGFR creat 45-59 ml/min/1.73 m 2 without markers of kidney damage, but with eGFR cys / eGFR creat-cys Z60 ml/min/1.73 m 2 could be considered not to have CKD. The removal of the diagnosis and label of CKD may be reassuring to patients and may help clinicians to focus their efforts on higher risk CKD patients.

The guideline statement suggesting the use of eGFR cys / eGFR creat-cys requires several important qualifiers. First, clinicians may not want or need to confirm the diagnosis of CKD in patients with eGFR creat 45-59 ml/min/1.73 m 2 without markers of kidney damage, either because the likelihood of CKD is high because of the presence of risk factors for CKD or presence of complications of CKD. Second, cystatin C is not universally available, so it may not be practical for a clinician to request a cystatin C blood test. Third, in certain clinical settings, the cost of measuring cystatin C (US $1-5) may be prohibitive. For all these reasons, the guideline statement 1.4.3.5 is stated as a suggestion.

In addition to the population described above, eGFR cys may be useful as a confirmatory test in situations where either the eGFR creat may be inaccurate or biased, or when the clinical scenario warrants a secondary test (Recommendation 1.4.3.2). In these clinical situations, a clearance measurement using an exogenous filtration marker may be optimal when it is available. The measurement of eGFR cys /eGFR creat-cys would be a relatively low-cost, feasible alternative when GFR measurement is not practical. The Work Group believed that measured urinary CrCl was an inferior confirmatory test relative to either GFR measurement or GFR estimation using both creatinine and cystatin C.

If cystatin C testing is desired, it is very important that clinicians understand principles of GFR estimation using cystatin C. As with creatinine, GFR should be estimated from cystatin C and an appropriate equation should be chosen for the specific clinical population (Recommendation 1. 4.3.6), and an assay be chosen for measurement that is traceable to the international standard reference material (Recommendation 1.4.3.7).

The utility of this specific statement to pediatrics is unclear as the vast majority of children with significant reductions in GFR, e.g., below 60 ml/min/1.73 m 2 , have either structural abnormalities or findings of renal damage as evidenced by urinary or serum abnormalities. It is very unlikely that isolated reduction in GFR would occur as in older adults. As such, the confirmation of CKD will be made on criteria beyond that of GFR alone. y Evaluated as the interquartile range for the differences between estimated and measured GFR.

Cystatin C is licensed for use in some countries in Europe and has been approved by the FDA as a measure of kidney function in the United States for nearly 10 years. In certain regions, notably Sweden and parts of China, eGFR is routinely estimated by both creatinine and cystatin C. As with creatinine, GFR estimates using cystatin C are more accurate in estimating measured GFR than the SCysC concentration alone. As with creatinine, sources of error in GFR estimation from SCysC concentration include non-steady state conditions, non-GFR determinants of SCysC, measurement error at higher GFR, and interferences with the cystatin C assays (Table 15 ).

For Recommendation 1.4.3.6, this guideline is fully applicable in pediatrics. See Recommendation 1.4.3.7 for details.

In terms of clinical settings where eGFR cys might be less accurate, it should be noted that Schwartz et al. determined that the only variable that explained the outlier values of estimated GFR (in both univariate and multivariate formulas) was heavier weight; race, high blood pressure, albumin levels and use of steroids did not contribute. 115 We recommend reporting serum cystatin C concentration rounded to the nearest 100 th of a whole number when expressed as conventional units (mg/l). When reporting eGFR cys and eGFR creat-cys :

We recommend that eGFR cys and eGFR creat-cys be reported and rounded to the nearest whole number and relative to a body surface area of 1.73 m 2 in adults using the units ml/min/1.73 m 2 .

We recommend eGFR cys and eGFR creat-cys levels less than 60 ml/min/ 1.73m 2 should be reported as ''decreased.''

As for SCr, reporting eGFR using cystatin C in addition to cystatin C will facilitate clinician's use of cystatin C for GFR estimation. It is important to acknowledge that calibration of assays is essential to interpretation of kidney function measures. Cystatin C is measured by a variety of immunoassays and, as for creatinine, there can be variation among methods in reported SCysC concentration but reported analytic variation appears less common than with creatinine. In June 2010 the Institute for Reference Materials and Measurements (IRMM) released a reference material (ERM-DA471/IFCC) for cystatin C measurement. Reagent manufacturers are in the process of recalibrating their assays against this standard which will enable standardized reporting of cystatin C and eGFR results. This recommendation is directed to laboratories with the intent to clarify the details of such calibration and the use of specific equations so as to facilitate international standardization.

Numerous equations have been developed to estimate GFR. Some equations include cystatin C as the only variable, while others include, age, sex, or race, but the magnitude of coefficients for these variables are smaller than in creatininebased equations, presumably reflecting less contribution of muscle to cystatin C generation than to creatinine generation. Equations without race are a potential advantage for cystatin C-based estimating equations in non-black, non-white populations.

For our review of GFR estimating equations, we only considered equations that were developed using assays that were traceable to the new reference methods and study populations in which SCysC concentration was measured using traceable assays. At this time, only the equations developed by CKD-EPI are expressed for use with standardized SCysC (Table 16 ), including equations developed in CKD populations in 2008 116, 117 and re-expressed for use with standardized cystatin C in 2011, and equations developed in diverse populations in 2012. 113 Equations using assays that are not traceable to the the reference standard are listed in Supplemental Table 3 .

The 2012 creatinine-cystatin C equation is more accurate than equations using creatinine or cystatin C separately (Figure 15 ), and more accurate than the 2008 creatinine-cystatin C equation (Table 17 ). The average of the GFR computed by the equations using creatinine and cystatin C separately is similar to the GFR computing using the creatinine-cystatin C equations. The 2012 cystatin C equation has similar accuracy to the 2009 creatinine equation described above but does not require use of race, and may be more accurate in non-black, non-white populations or in clinical conditions with variation in non-GFR determinants of SCr. We anticipate the development of additional equations using cystatin C in the future and recommend that they be compared with the CKD-EPI 2012 cystatin C and creatinine-cystatin C equations as well as with the CKD-EPI 2009 creatinine equation.

For Recommendation 1.4.3.7 this set of statements would need to be altered for application in pediatric practice in the following way: K Measure SCysC using an immunonephelometrically determined method in which the assay is calibrated and traceable to the international standard reference material.

K Report eGFR cys in addition to the SCysC concentration in children.

K Report eGFR cys in children specifying the specific equation used.

Based on their recent work comparing particle-enhanced nephelometric to turbidometric immunoassays for cystatin C in a pediatric population with significant reduction in GFR (median GFR B45 ml/min/1.73 m 2 ), Schwartz et al. demonstrated less bias for the nepholometric value and that its reciprocal showed a substantially improved correlation to the iohexol GFR (0.87 versus 0.74) when compared to that of the turbidometric assay. 115 This demonstrates the importance of using an assay calibrated and traceable to the international standard reference material. Numerous pediatric specific and derived eGFR cys formulas have been published, the most current and recent by Schwartz 115 who derives the newest available from a validation set from the CKiD study and compares those results to 3 other well-recognized formulas from the literature, namely Zapitelli et al., 118 Filler and Lepage, 119 and Hoek et al. 120 Their results demonstrate that the newest univariate cystatin C formula derived from the CKiD cohort has excellent accuracy with 82.6% of eGFR cys within 30% of the true measured iohexol GFR and 37.6% within 10% of the true measured iohexol GFR. Likewise the bias of 0.3% and correlation of 0.85 are the best of all formulas reported to date. The formula they use to obtain these values is: 70.69 Â (cystatin c) -0.931 .

Of note, their final multivariate equation, when applied to the validation set and using height/SCr, nepholemetric cystatin C, BUN, sex, and an adjusted height term demonstrated the best accuracy reported in pediatric studies to date, 91% and 45% within 30% and 10% of the true GFR, respectively; with a bias of only À0.2 and correlation of 0.92.

1.4.3.8: We suggest measuring GFR using an exogenous filtration marker under circumstances where more accurate ascertainment of GFR will impact on treatment decisions. (2B)

In clinical practice, there may be a requirement to measure GFR when the need for a 'truer' more precise value is identified (such as for organ donation or for dosing of toxic drugs). The intention of this statement is to recognize that specialty centers for kidney disease, usually tertiary referral centers, should have the capacity to measure GFR using exogenous filtration markers as a recognized specialist service. We recognize that this ability does not currently constitute the definition of specialty kidney referral centers and that it may be problematic, but resources to ensure accurate measurement ought to be made available. Given that these specific measurements require levels of rigor and reproducibility similar to those of laboratory calibration issues, specialist centers would be the right place to suggest that these facilities be made available.

GFR is measured as the clearance of an exogenous filtration marker. The ''gold standard'' method is the urinary clearance of inulin during a continuous intravenous infusion. To simplify the procedure there are a number of alternative clearance methods and alternative filtration markers, with minor differences among them. 79 For all measurement methods, measured GFR should be reported as described for eGFR. Table 18 summarizes the strengths and limitations of clearance methods and filtration markers for clearance measurements. Thus measured GFR may also be associated with error, and in evaluation of GFR estimating equations, random error in GFR measurement is a source of some of the imprecision in GFR estimating equations. 27, 121 In principle, the magnitude of random error in GFR measurements is likely to be smaller than errors in GFR estimation using creatinine and cystatin C due to conditions listed in Tables 11 and 15 .

International Relevance

The calculation of eGFR using these equations usually requires computer programming and some processes for quality monitoring. Nonetheless the statements are here to serve as 'best practice' recommendations so that these can be c h a p t e r 1 aspired to over time in those locations where these recommendations are currently not able to be implemented. The Work Group appreciated that not all laboratories have capabilities to assay cystatin C. Different countries and regions will have different availabilities for measurement of GFR. The statement about GFR measurements mostly applies to countries with tertiary care services such as kidney transplantation and oncology.

Implications for Clinical Practice and Public Policy

It is important for clinicians to understand various methods for estimating and measuring kidney function and the situations in which specific methods may be superior in clinical decision making about treatment and referral.

Standardized assays and robust equations are important for epidemiological and planning purposes so that public policy can be informed by more accurate estimates of CKD, which may be possible with improved standardization of both assays and equations.

In different parts of the world, different assays are used and equations for estimating eGFR may differ. Thus, appreciating and understanding local standards is important for individual patients who may travel, and for comparative research across countries or regions.

In the event that a clinician requires measurement of GFR instead of an estimate, knowledge of these different tests and availability of them is important. Situations in which measurement would be required are likely quite infrequent c h a p t e r 1 but include donor evaluation in kidney transplantation and use of toxic drugs which have a narrow therapeutic range. We acknowledge that drug development and clinical observation programs may not define the various thresholds with sufficient granularity to require greater accuracy than is provided by eGFR creat . Guidance is evolving regarding kidney function evaluation during drug development programs. 13 here are no direct implications for public policy for the statement about GFR measurement.

Areas of Controversy, Confusion, or Non-consensus

The Work Group recognizes that no single creatinine-based estimating equation will perform optimally in all clinical circumstances and that there may be changes in the performance of estimating equations over time and in different regions. However, for the purpose of eGFR reporting, it is important to select a single equation within a region or country. At the writing of this guideline, in North America, Europe, and Australia, the advantages of the CKD-EPI equation at higher GFR make it more applicable than the MDRD Study equation for general practice and public health.

While cystatin C offers some advantages over SCr as the basis of estimating equations, the cost of the assay and potential lack of standardization across laboratories for this 'newer' test limit our ability to recommend it as a preferred or even usual second test after creatinine. We recognize that these factors may lead to variations in implementation. The recommendation to consider confirmatory or additional testing if there is a need for more accurate determination of GFR is important. That there are other laboratory markers to estimate GFR (i.e., cystatin C) is stated here as there has been accumulating data to support its use in these situations. We have specifically mentioned cystatin C because of these data.

Clarification of Issues and Key Points

It is important for clinicians to appreciate the need for standardized assays and standardized equations for laboratory reporting of eGFR. Changes in laboratory assays or calculation methods should be reported to clinicians in order to avoid confusion when serially following individuals. This is because values in an individual might indicate a worsening or improvement in eGFR which may be attributable to different assays or calculation methods, rather than a reflection of true change.

When precise information about GFR is required, direct measurement using reliable methods should be pursued.

For Recommendation 1.4.3.8 this guideline is fully applicable in pediatrics.

1.4.4 Evaluation of albuminuria

1.4.4.1: We suggest using the following measurements for initial testing of proteinuria (in descending order of preference, in all cases an early morning urine sample is preferred) (2B):

(1) urine albumin-to-creatinine ratio (ACR);

(2) urine protein-to-creatinine ratio (PCR);

(3) reagent strip urinalysis for total protein with automated reading; (4) reagent strip urinalysis for total protein with manual reading. 1. 4

We recommend measurement of urinary albumin because it is relatively standardized and because it is the single most important protein lost in the urine in most chronic kidney diseases. Use of urinary albumin measurement as the preferred test for proteinuria detection will improve the sensitivity, quality, and consistency of approach to the early detection and management of kidney disease. By contrast, laboratory tests purporting to measure urinary total protein are commonly flawed, often being standardized against, and predominantly sensitive to, albumin. They have poor precision at low concentrations and demonstrate poor between-laboratory agreement while being insensitive, non-specific, and susceptible to a range of falsepositive and false-negative problems. There may occasionally 56 Kidney International Supplements (2013) 3, 19-62 c h a p t e r 1 be clinical reasons for a specialist to use PCR instead of ACR to quantify and monitor significant levels of proteinuria (e.g., in patients with monoclonal gammopathies).

Commonly used reagent strip devices measuring total protein are insufficiently sensitive for the reliable detection of proteinuria, do not adjust for urinary concentration, and are only semi-quantitative. Furthermore, there is no standardization between manufacturers. The use of such strips should be discouraged in favor of quantitative laboratory measurements of albuminuria or proteinuria. When used, reagent strip results should be confirmed by laboratory testing (Figure 16 ).

The combination of reagent strips with automated reader devices can improve inter-operator variability. More recently launched reagent strip devices capable of producing albumin or total protein results as a ratio to urinary creatinine require further evaluation to provide evidence that they have equivalent sensitivity and specificity to laboratory tests and are economically advantageous.

Although the reference point remains the accurately timed 24-hour specimen, it is widely accepted that this is a difficult procedure to control effectively and that inaccuracies in urinary collection may contribute to errors in estimation of protein losses. In practice, untimed urine samples are a reasonable first test for ascertainment of albuminuria. An EMU ('first pass') sample is preferred since it correlates well with 24-hour protein excretion, has relatively low The concentration of protein or albumin in a urine sample will be affected by hydration (i.e., how diluted or concentrated a urine sample is). Creatinine excretion is considered to be fairly constant throughout the day and it has become customary to correct for urinary concentration by expressing either the protein or albumin concentrations as a ratio to the creatinine concentration in the same sample.

Timed urine collections may be used for confirmatory purposes but are not required except in circumstances in which untimed urine ACR is less accurate. It is worthwhile noting that albumin and protein excretion display considerable biological variability and may be increased by a variety of pathological and non-pathological factors. Consequently, confirmation of increased excretion rates is recommended.

Why is albumin measurement being recommended instead of total protein? 4] [125] There is substantial evidence linking increased albuminuria to outcomes of CKD 4, 30 ). ] [128] [129] In health, relatively small amounts of albumin (o30 mg/ 24 hours) are lost in the urine. Because of this, and additionally because total protein assays are imprecise and insensitive at low concentrations, relatively large increases in urine albumin excretion can occur without causing a significant measurable increase in urinary total protein. 125 otal protein measurement is problematic in urine due to: large sample-to-sample variation in the amount and composition of proteins; high and variable concentrations of non-protein interfering substances relative to the protein concentration; and high inorganic ion content. All these factors affect the precision and accuracy of the various methods. Most laboratories currently use either turbidimetry or colorimetry 130 to measure total protein and as with urine reagent strip analysis, these methods do not give equal analytical specificity and sensitivity for all proteins which can contribute to diverse estimates of proteinuria prevalence. 131, 132 7] [138] . There is no reference measurement procedure and no standardized reference material for urinary total protein listed by the JCTLM. 0] [141] Since a variable mixture of proteins is measured, it is difficult to define a standardized reference material.

How should albumin be measured and reported?

Albumin should be measured using immunological assays capable of specifically and precisely quantifying albumin at low concentrations and of producing quantitative results over the clinically relevant range. Currently urinary albumin is predominantly measured by diagnostic laboratories using turbidimetric assays. 130 At present there is no reference measurement procedure or standardized reference material for urine albumin listed by the JCTLM, although the NKDEP and the International Federation of Clinical Chemistry and Laboratory Medicine have recently established a joint committee to address these issues. 142, 143 At present, most assays are standardized against a serum-based calibrant (CRM 470) distributed by the IRMM of the European Commission, as has previously been recommended by KDIGO. 31 lbumin concentration should be reported as a ratio to urinary creatinine concentration (mg/mmol or mg/g). ACR results should be expressed to one decimal place (mg/mmol) or whole numbers (mg/g). Both enzymatic and Jaffe assays are suitable for the measurement of creatinine in urine. We suggest that the term 'microalbuminuria' no longer be used because it can be misleading in suggesting that the albumin may be small or different in some way. The proposed albuminuria categories A1-3 are a more clinically meaningful way to express information about categories within the continuum of albumin excretion.

Reagent strip point-of-care testing devices capable of measuring low concentrations of albumin are also available producing both semi-quantitative and fully quantitative ACR results. 9] [150] While studies of these devices have been somewhat limited in size, they demonstrate their potential to play a significant role in the care pathway of patients suspected of having CKD.

Why are reagent strip devices for protein measurement considered less accurate than laboratory measurement?

Reagent strip devices for proteinuria detection have been in use for more than 50 years. As discussed earlier, a positive reagent strip result is also associated with outcomes of CKD. Such devices have been used to support screening programs in some countries, [151] [152] [153] although there appears to be no evidence supporting such screening of unselected populations. 154 6] [157] There is evidence that strips from different manufacturers perform differently at the cutoff (' þ ') concentration of 300 mg/l and degrees of 'plusness' between different manufacturers don't always correspond to the same nominal concentration of protein in urine. 124 Concentrated urines may give a color change in the positive range of a reagent strip device even though protein loss remains normal and vice versa. False-positive results may occur if the urine is alkalinized (e.g., due to urinary tract infection) or in the presence of quaternary ammonium compounds that alter the pH of the urine. The performance of reagent strips is operator-dependent 158 and affected by the presence of colored compounds such as bilirubin and certain drugs (e.g., ciprofloxacin, quinine, and chloroquine). 159 eagent strips cannot reliably distinguish between proteinuria categories 124, 157 and show relatively poor diagnostic accuracy for proteinuria detection. 160, 161 In the Australian Diabetes, Obesity and Lifestyle (AusDiab) study, a reagent strip reading of þ or greater had 58% and 99% sensitivity for detecting ACR Z30 mg/g (Z 3 mg/mmol) and Z300 mg/ g (Z30 mg/mmol), respectively. 47% of individuals who tested þ or greater had an ACR Z30 mg/g (Z 3 mg/mmol) on laboratory testing. 162 utomated devices capable of reading the color changes of reagent strips using reflectance spectrometry are available. These reduce inter-operator variability and improve diagnostic accuracy. 150, 158, 163 A creatinine test pad has been added to some reagent strip systems to enable a PCR to be reported and so reduce the intra-individual variation seen with random urine collections. Such devices have been shown to be suitable for ruling out significant proteinuria (4300 mg/ 24 hours) in an outpatient setting. 149 orrecting for urinary dilution. Since creatinine excretion in the urine is fairly constant throughout the 24-hour period, measurement of ACR (or PCR) allows correction for variations in urinary concentration. 164, 165 [173] [174] [175] [176] [177] Expressing albumin as a ratio to creatinine reduces intraindividual variability: lowest variability for the ACR has been reported in EMU samples as opposed to other untimed samples or timed collections. 142, 178 In one study albumin variability was reduced from 80% to 52% when expressed as an ACR rather than an albumin concentration. 179 The within-subject biological variation for urinary ACR in an EMU has been reported to be 31%, compared to 36% for urinary albumin concentration. 180 The same study reported variability for ACR of 103% and 85% in random and timed 24-hour collections, respectively. 180 Intra-individual variation for protein loss is also significantly reduced when reported as a PCR compared to protein concentration in random urine samples collected throughout the day (a mean reduction from 97% to 39%). 179 y and how should a finding of albuminuria be confirmed?

Given the high biological variation and other pathological and physiological causes of albuminuria (Table 19 ), 143 repeat testing to confirm albuminuria, ideally using an EMU and laboratory testing, is recommended (Figure 16 ).

There has been extensive discussion in the literature about the appropriate urine sample to use for the investigation of protein loss. It is generally recognized that a 24-hour sample is the definitive means of demonstrating the presence of proteinuria. However, overnight, first void in the morning (i.e., EMU), second void in the morning, or random sample collections can also be used. In a systematic review random urine PCR was shown to have better performance as a test for ruling out significant proteinuria than as a ''rule-in'' test; the authors suggested that positive PCR results may still require Upright posture (orthostatic proteinuria) 41, 183 Other conditions increasing vascular permeability (e.g., septicemia) Intraindividual variability Intrinsic biological variability 180 Genetic variability 184

Preanalytical storage conditions

Degradation of albumin before analysis a Non-renal causes of variability in creatinine excretion Age (lower in children and older people) Race (lower in Caucasian than black people) Muscle mass (e.g., lower in people with amputations, paraplegia, muscular dystrophy) Gender (lower in women) Changes in creatinine excretion Non-steady state for creatinine (AKI)

Analytical factors

Antigen excess ('prozone') effect Samples with very high albumin concentrations may be falsely reported as low or normal using some assays 124 Abbreviations: ACR, albumin-to-creatinine ratio; AKI, acute kidney injury; UTI, urinary tract infection.

a Samples for urinary albumin (or total protein) measurement may be analyzed fresh, stored at 41C for up to one week, or stored at -701C for longer periods. Freezing at -201C appears to result in loss of measurable albumin and is not recommended. When analyzing stored samples, they should be allowed to reach room temperature and thoroughly mixed prior to analysis. 142 onfirmation with a 24-hour collection. 185 If an EMU is unavailable, subsequent samples can give a reliable indication of the 24-hour urine protein loss. 174

The recommendation to replace urinary total protein with albumin as the test of choice in testing for proteinuria is consistent with most, 1, 31, 130, 186, 187 but not all, 188, 189 current national and international guidance. It is accepted that cost pressures may affect implementation of this recommendation and may differ across the world.

0] [191] Nevertheless, in the present guideline we acknowledge that these devices may have a role, particularly in settings where access to laboratory services may be limited.

ACRs in North America tend to be reported in mg/g whereas in other parts of the world usage of mg/mmol predominates. This difference appears unlikely to be resolved in the foreseeable future. When publishing data authors should ensure either that both units are cited or that a conversion factor is provided.

There is increasing adoption of the term 'albuminuria' instead of microalbuminuria by international and national laboratory and some clinical organizations.

Direct reagent costs of total protein measurement are generally lower than those of albumin measurement, which requires antibody-based reagents. It is often considered that reagent strip analyses are a cheaper option. Therefore some health-care systems may struggle to justify the recommendations in this guideline.

Costs of diagnostic tests vary depending on local financial agreements between hospitals and suppliers. In England, the National Institute for Health and Clinical Excellence (NICE) sampled a small random number of laboratories and estimated the average cost of an ACR to be d2.16 whereas a PCR cost d1.42. 186 It is acknowledged that increased use of ACR testing may reduce the unit cost on the basis of economies of scale. In Canada, laboratory analysis costs (Canadian dollars) of $2.81 for reagent strip, $11.67 for PCR, and $29.23 for ACR have been cited. 192 In relation to albumin-specific reagent strips, a cost of approximately $4 for a Micral test II (Roche Diagnostics) compared to $2 for a laboratory ACR has been reported. 193 he cost-and clinical-effectiveness of an approach utilizing reagent strip testing followed by laboratory measurement compared to an approach in which samples are submitted directly to the laboratory (for either albumin or protein measurement) has recently been evaluated in a health economics model. 186 The model favored abandoning the use of reagent strips for identification of proteinuria.

Some data suggest that ACR is a poorer predictor of 24-hour total protein loss than PCR 194 and has no advantage over PCR as a predictor of renal outcomes and mortality in patients with CKD. 195, 196 In the prediction of future transplant rejection, PCR has been reported to have equal utility to ACR, 192 although in a separate study ACR was found to be a better predictor. 197 n the setting of preeclampsia, proteinuria is generally defined as Z300 mg/24 hours or a PCR Z300 mg/g (Z30 mg/mmol). 175 Currently, there is insufficient evidence to substitute urine albumin measurement for total protein in this setting. 172 reatinine excretion is affected by a variety of non-renal influences (Table 19 ) and it therefore follows that different cutoffs for ACR (and PCR) may be required in different individuals. 194, 198 While age-related cutoffs have not generally been applied in clinical practice, clinicians should bear this in mind when interpreting urine ACR data in older individuals or those with very low body mass, as these will impact the urine creatinine excretion.

While most guidelines agree that an ACR greater than approximately 3 mg/mmol (30 mg/g) is pathological in the setting of diabetes, in the non-diabetic population a higher threshold has commonly been used to define proteinuria. In the NICE guideline in England and Wales, proteinuria in nondiabetic individuals was defined as Z30 mg/mmol (Z300 mg/g), with higher level proteinuria being 470 mg/mmol (4700 mg/ g). 186 Confirmation of results lying between 30 and 70 mg/mmol (300-700 mg/g) was recommended. 186 The present guideline proposes a lower threshold definition for albuminuria for use in both diabetic and non-diabetic individuals.

A study from Italy in type 2 diabetes has reported that, although intra-individual biological variation of albuminuria is large, a single sample (either ACR or timed collection) can accurately classify patients into albuminuria categories, negating the need for multiple collections. 178 ome data suggest that a significant proportion of albumin present in urine may be non-immunoreactive, [199] [200] [201] [202] although this finding has been questioned. 203, 204 here is a substantial existing literature using the term microalbuminuria and many existing guidelines use this term especially in the context of diabetes and cardiovascular risk, as its presence confers risk. Nonetheless, the Work Group believes that it is important for this international guideline to foster 'best practices' and clarity of communication, and since the risk of adverse events is continuous throughout the spectrum of albuminuria, we encourage adoption of the term 'albuminuria' with subsequent quantification of the level or amount.

For Recommendation 1.4.4.1, this set of statements would need to be altered for application in the pediatric practice as follows:

We suggest using the following measurements for initial testing of proteinuria in children (in descending order of preference):

(1) urine PCR, EMU sample preferred;

(2) urine ACR, EMU sample preferred;

(3) reagent strip urinalysis for total protein with automated reading; (4) reagent strip urinalysis for total protein with manual reading.

For Recommendations 1.4.4.2 and 1.4.4.3, this set of statements would need to be altered for application in the pediatric practice as follows:

Currently the urinary PCR should be favored over the urine ACR in children. Unlike in adults where powerful evidence exists in support of the use of measures of albumin rather than total protein to predict adverse outcomes, this level of evidence is currently lacking in children. 205 However, current longitudinal trials such as CKiD 55 and European 4C 78 may eventually shed light on this issue.

In children the underlying conditions associated with the diagnosis of CKD are also important considerations as to which form of testing is most valuable. Unlike adults where the majority of patients with CKD are attributed to an underlying glomerular disease or hypertensive damage, the vast majority of children have underlying developmental abnormalities often referred to as CAKUT (congenital anomalies of the kidney and urinary tract). 70 This relative paucity of glomerular conditions makes the use of albumin excretion a less sensitive test for diagnostic purposes as many children will have underlying tubular conditions and hence tend to excrete more Tamm-Horsfall protein and other lowmolecular-weight proteins that will not be captured by the albumin-to-creatinine (or formal albumin excretion) assay.

For Recommendations 1.4.4.2 and 1.4.4.2.1 this guideline is fully applicable in pediatrics. The recommendation that clinical laboratories report ACR and PCR in untimed urine samples in addition to albumin concentration or proteinuria concentrations rather than the concentrations alone is valid and useful in the pediatric population. As per Recommendation 1.2.4, however, note should be made that age-related normal values for urinary protein losses must be considered when laboratories choose to report either ACR or PCR.

Albuminuria in children, whether measured as an absolute value per day, an excretion rate, or as an albumin to creatinine ratio is fraught with more uncertainity than in adults as they are known to vary across categories of age, sex, height, weight, and Tanner staging. 206 n two recent reviews by Rademacher 206 and Tsioufis et al., 205 both groups examined the results of all relevant studies on normative values of AER or ACR. Rademacher's paper in particular provides detailed information on the mean AER values (with SD) across a variety of studies, ages, sex, and race, and provides a normative estimate for overnight AER of between 2-6 mg/minute or a 95 th percentile value from 4.5-28 mg/ minute. Similarly, they summarize results for ACR in normal children and suggest that the mean for children older than 6 years would seem to fall between 8-10 mg/g (0.8-1.0 mg/mmol).

For Recommendation 1.4.4.3, this guideline is fully applicable in pediatrics.

1.4.4.4:

If significant non-albumin proteinuria is suspected, use assays for specific urine proteins (e.g., a 1 -microglobulin, monoclonal heavy or light chains, [known in some countries as ''Bence Jones''proteins]). (Not Graded)

Testing for tubular proteinuria using a total protein approach almost certainly has very poor sensitivity for detecting tubular disease. When an isolated tubular lesion is suspected (Table 3 ), this is probably best investigated by measuring a specific tubular protein (e.g., a 1 -microglobulin) using an immunoassay approach.

There have been concerns that replacing urinary total protein measurement with albumin measurement may cause nonalbuminuric (effectively tubular and overproduction) proteinuria to be missed. Low-molecular-weight proteinuria is a defining feature in some uncommon kidney diseases (e.g., Dent's disease). 207 However, for some of the reasons already discussed, total protein assays will also be poor at detecting tubular proteinuria. When investigating patients for tubular proteinuria, it is advisable to use assays targeted at specific tubular proteins.

In the AusDiab study, of those with proteinuria (2.4% of the general population, defined as a PCR 423 mg/mmol [230 mg/ g]) 92% had albuminuria (defined as an ACR 43.4 mg/mmol [34 mg/g] ); 8% had an ACR within the reference range. 208 These individuals were less likely to have diabetes than those with both proteinuria and albuminuria, but no further information is available as to the nature of the proteinuria in these individuals or its likely significance. The authors speculate that these individuals could have had light chain proteinuria or interstitial nephropathies. Using albuminuria testing to identify proteinuria had a specificity of 95%. The negative predictive value was 99.8% and the positive predictive value was 32.4%. The authors concluded that testing for albuminuria rather than proteinuria was supported.

As discussed above, quite significant increases in urinary albumin loss have to occur before such an increase is detectable on the background of a total protein assay. The situation is even more extreme for tubular proteins which, in health, are present in urine at lower concentrations than albumin (e.g., normal daily losses of retinol binding protein, a 1 -microglobulin and b 2 -microglobulin are 0.08, 3.6, and 0.1 mg/d, respectively). 209 This problem will be exacerbated by the fact that the recognition of tubular proteins by some total protein assays is poor. 210 n disease states concentrations of tubular proteins, at least collectively, can reach levels detectable by total protein assays. For example, among patients with tubulointerstitial disease but without renal insufficiency, median concentrations of a 1microglobulin were 37 mg/l, with concentrations up to 100 mg/l being observed; higher concentrations were seen in patients with decreased GFR. 211 Among a group of patients with acute tubular necrosis requiring dialysis treatment, median a 1microglobulin concentration was 35 mg/mmol of creatinine. 212 owever, although tubular proteinuria is characterized by a relative increase in low-molecular-weight protein concentrations, generally albumin still remains a significant component of the total protein concentration. Indeed, it is thought that tubular disease results in an increase in albumin loss as a result of decreased tubular reabsorption of filtered albumin. For example, it has been estimated that when tubular absorption fails completely, b 2 -microglobulin loss increases to 180 mg/24 hours (approximately 1800-fold normal) but there will also be an increase in urinary albumin loss to about 360 mg/24 hours (approximately 20-fold normal). 209 In a series of patients with Dent's disease, a classical tubular disorder, 21 of the 23 patients demonstrating increased urinary a 1 -microglobulin and b 2microglobulin loss also had increased urinary albumin loss: those who did not had borderline increases in tubular protein losses that would not have been detectable using a total protein measurement approach. 207 The authors comment that in those patients in whom proteinuria was marked (41 g/d), urinary albumin loss was also markedly increased. In some situations, however, tubular proteinuria in the absence of albuminuria has been reported (e.g., in some children with type 1 diabetes 213 and in kidney scarring in reflux nephropathy 214 ).

There is no reason to believe that there are significant differences around the world with respect to incidence or prevalence of conditions in which measurement of nonalbumin proteins would be required. The availability of reliable tests for these alternative proteins, however, may be different in different regions.

The incidence and prevalence of tubular disorders will vary geographically with the clinical setting (e.g., adult or pediatric practice) and factors such as occupational exposure. Clinicians should agree with their local laboratories a suitable approach to the detection of tubular proteinuria and laboratories should be able to advise on suitable sample handling procedures. It is acknowledged that many laboratories do not currently offer assays of tubular proteins.

In patients with suspected myeloma, monoclonal heavy or light chains (known in some countries as Bence Jones) protein should be sought in concentrated urine using electrophoresis with immunofixation of any identified protein bands in accordance with current myeloma guidelines. 215 Simultaneous albumin measurement is needed when the possibility of immunoglobulin light chain (AL) amyloid or light chain deposition disease is suspected.

Non-albumin proteinuria may also be suspected in patients with disorders of tubular function (see Table 3 ).

Testing for proteinuria using a urine albumin rather than total protein first-line approach may occasionally miss cases of tubular proteinuria but the significance of this problem is probably overestimated and should be the subject of further research.

Earlier guidance from KDOQI 1 suggested that proteinuria in children should be detected with total protein rather than albumin assays due to the higher prevalence of nonglomerular diseases in this group of patients. For the reasons outlined above, we do not think total protein assays are suitable for this purpose and would ideally recommend testing for albumin and for specific tubular proteins when non-glomerular disease is suspected.

For Recommendation 1.4.4.4, this statement is fully applicable in pediatrics. In children the likelihood of any form of overflow proteinuria such as seen in conditions of heavy or light chain production is extremely low; however a significant number of underlying genetic tubular disorders do exist and protein electrophoresis can assist the practitioner in determining the presence of such a condition or the concurrent finding of severe tubular injury in addition to a glomerular condition.

DISCLAIMER

Chapter 2: Definition, identification, and prediction of CKD progression Kidney International Supplements (2013) 3, 63-72; doi:10.1038/kisup.2012.65

2.1: DEFINITION AND IDENTIFICATION OF CKD PROGRESSION

2.1.1: Assess GFR and albuminuria at least annually in people with CKD. Assess GFR and albuminuria more often for individuals at higher risk of progression, and/ or where measurement will impact therapeutic decisions (Figure 17 ). (Not Graded)

The statement is worded this way to remind the practitioner to use both GFR and albuminuria in order to assess progression and is consistent with the definition offered in Chapter 1 regarding definitions of CKD which include both parameters. There is increasing evidence which supports that both parameters are valuable. Lower GFR and greater albuminuria are both associated with an increased rate of progression and are synergistic. More frequent measures of eGFR and albuminuria should be considered in patients with a lower GFR and greater albuminuria as these people are more likely to progress. Frequency of measurement should also be individualized based on the patient history and underlying cause of kidney disease.

In specific conditions (e.g., GN or increased levels of albuminuria), frequent (every 1-3 months) assessment may guide therapeutic decisions. Regular monitoring of stable patients may include more frequent monitoring than annually, but will be dictated by underlying cause, history, and estimates of GFR and ACR values obtained previously.

There is variability in the presence of or rate of decline of kidney function in those with CKD. The rate at which http://www.kidney-international.org c h a p t e r 2 Figure 17 | GFR and albuminuria grid to reflect the risk of progression by intensity of coloring (green, yellow, orange, red, deep red). The numbers in the boxes are a guide to the frequency of monitoring (number of times per year). Green reflects stable disease, with follow-up measurements annually if CKD is present; yellow requires caution and measurements at least once per year; orange requires measurements twice per year; red requires measurements at 3 times per year while deep red may require closest monitoring approximately 4 times or more per year (at least every 1--3 months). These are general parameters only based on expert opinion and must take into account underlying comorbid conditions and disease state, as well as the likelihood of impacting a change in management for any individual patient. CKD, chronic kidney disease; GFR, glomerular filtration rate. Modified with permission from Macmillan Publishers Ltd: Kidney International. Levey AS, de Jong PE, Coresh J, et al. 30 The definition, classification, and prognosis of chronic kidney disease: a KDIGO controversies conference report. Kidney Int 2011; 80: 17-28; accessed http://www.nature.com/ki/journal/v80/n1/full/ki2010483a.html this decline occurs also varies based on the underlying population, cause of CKD, presence of albuminuria/proteinuria, comorbidities and age. The Work Group searched the literature for longitudinal studies that evaluated decline in kidney function. As outlined in Table 20 the study populations included healthy adults, those with comorbidity, as well as a subgroup of adults aged 65 and older.

Data from the PREVEND study, a prospective, population-based cohort study, provides important information on decline in kidney function at the population level. 219 he PREVEND study evaluated 6894 people over a 4-year period and reported loss in eGFR of 2.3 ml/min/1.73 m 2 / 4 years in the whole population, 7.2 ml/min/1.73 m 2 /4 years in participants with macroalbuminuria (4300 mg/24 hours) and 0.2 ml/min/1.73 m 2 /4 year in participants with impaired renal function. The yearly decline in eGFR among a Japanese general population over 10 years was slightly lower at 0.36 ml/min/1.73 m 2 /year. 220 The rate of eGFR decline was approximately two times higher in participants with proteinuria, and about 1.5 times higher among participants with hypertension. 220 Among adults aged 65 and older, progression (median follow-up 2 years) varied by sex and presence of diabetes. 223 In general these studies suggest progression rates of approximately 0.3 to 1 ml/min/1.73 m 2 / year among participants without proteinuria or comorbidity and rates of approximately two to three times higher among participants with proteinuria or comorbidity. The somewhat surprising finding that eGFR had low rates of progression among the group with impaired renal function at baseline 219 has been shown in other studies 225 and may relate to the statistical phenomenon of regression to the mean. There is also a concern that it is hard to maintain consistent calibration of the SCr assay over time and progression results are highly sensitive to drift in the creatinine assay.

Studies evaluating rate of decline in eGFR among populations with CKD specifically are outlined in Table 21 and typically demonstrate a slightly more rapid rate of decline in this subgroup, thus requiring more frequent assessment of GFR and albuminuria.

Data from the MDRD Study during a mean 2.2 year follow-up showed that the average rate of decline in GFR ranged from 2.3 to 4.5 ml/min/year, depending on the baseline GFR and protein/MAP treatment assignments. 227 imilarly, a more recent study of 4231 patients with GFR categories G3a-G5 (GFRo60 ml/min/1.73 m 2 ) referred to a nephrologist showed a mean decline in GFR of 2.65 ml/min/ 1.73 m 2 /year, 231 and variability in the rates of decline in this referred cohort.

Note that there have been no studies which evaluate the utility of more or less frequent monitoring in CKD cohorts.

Frequency of measurements of GFR and albuminuria may vary by country and so are economic resources available to support such testing, and the ability to implement therapeutic strategies to address changes. Nonetheless, given the availability of simple monitoring tools like urine reagent 216 Healthy kidney donors 141 0.40 ml/min/year Rowe JW et al. 217 Healthy males 293 0.90 ml/min/1.73 m 2 /year (CrCl) Lindeman RD 218 Healthy males 254 0.75 ml/min/year (CrCl) Halbesma N et al. 219 PREVEND cohort (all participants) 6894 0.55 ml/min/1.73 m 2 /year Imai E et al. 220 Annual health exam participants in Japan 120,727 0.36 ml/min/1.73 m 2 /year Matsuchita K et al. 221 Atherosclerosis Risk In Communities Cohort 13,029 0.47%/year (median) Kronborg J et al. 222 Healthy adults from Norway 4441 1.21 ml/min/1.73 m 2 /year (men) 1.19 ml/min/1.73 m 2 /year (women) With comorbidity Lindeman RD 218 Males with renal/urinary tract disease 118 1.10 ml/min/year (CrCl) Lindeman RD 218 Males with hypertension 74 0.92 ml/min/year (CrCl) Halbesma N et al. 219 PREVEND cohort -adults with macroalbuminuria (4300 mg/24 hours) 86 1.71 ml/min/1.73 m 2 /year Halbesma N et al. 219 PREVEND strips, consideration may be given to implementation of this assessment in high-risk groups.

Practitioners must incorporate underlying category of GFR and albuminuria as well as cause of kidney disease and individual patient characteristics in determining the frequency of ongoing assessment. The implications for practice include the incorporation of regular monitoring of both GFR and albuminuria into clinical care for patients with CKD. There are no immediate implications for public policy of this statement.

There are many who would like more definitive guidance on frequency of measurement according to specific categories of risk. However this is not possible at the current time given the lack of evidence to guide such statements and the extreme number of individual circumstances that would mitigate any proposed protocol.

We recommend further research to more accurately define the frequency with which GFR and albuminuria measure-ments should be performed based on their ability to inform strategies which prevent adverse outcomes (e.g., progression of kidney disease and death).

a) Assessment of both GFR and albuminuria should be undertaken to evaluate progression. b) More frequent assessment is required as kidney disease progresses. c) Not all individuals with CKD require close surveillance and monitoring; clinical context remains an important modifier for all recommendations. d) While cause of CKD is an important predictor of progression, it is the values of GFR and albuminuria that are used to assess progression.

Currently there is no evidence as to the value of increasing the frequency of assessment of either GFR or proteinuria in children with CKD. Eventually more complete longitudinal data from the CKiD cohort 55 and hence better granularity of individual and group rates of decline in GFR may provide the data required to strengthen proof of this guideline in children. As described in detail in the Pediatric Considerations for Recommendation 1.3.1, there is good observational evidence acknowledging the importance of level of GFR and proteinuria at baseline on predicting rates of progression and it may be that interventional opportunities would exist if closer monitoring and earlier recognition of worsening in these values for the individual were available. Future studies may examine this. K Rapid progression is defined as a sustained decline in eGFR of more than 5 ml/min/1.73 m 2 /year.

K The confidence in assessing progression is increased with increasing number of serum creatinine measurements and duration of follow-up.

This statement serves to inform clinicians that some consistent definition of progression is required and should be implemented based on an appreciation of baseline values for an individual. There is considerable controversy as to what constitutes normal progression of CKD. The potential for biological and analytical variation associated with use of SCr measurements should be taken into account as they represent reversible fluctuations in GFR and are not necessarily indicative of progression. Further, it is important to recognize that the degree of precision with which progression is able to be estimated is highly dependent upon two factors: the number of SCr measurements used to define progression and the duration of follow-up. Estimating risk of ESRD based on extrapolation of the previous rate of change in GFR required substantial information (Z4 measurements over Z3 years in most cases) to add to the risk information in the most recent GFR. Further, it should be recognized that some reno-protective treatments (e.g., BP lowering and RAAS antagonists) result in a slower rate of GFR decline longterm but often lower GFR in a stepwise fashion as a result of hemodynamic effects. Even substantial (5-25%) reductions in GFR may be protective, complicating the interpretation of progression in these individuals. Finally, underlying disease activity should be considered when assessing patients for progression of kidney dysfunction.

The importance of determining the rate of decline in kidney function over time is to identify individuals who are progressing at a more rapid rate than anticipated, which is associated with increased morbidity and mortality. Individuals who are ''rapid progressors'' should be targeted to slow their progression and associated adverse outcomes. A progressive decline in kidney function is influenced by baseline GFR category and albuminuria category.

Unfortunately few studies are available to guide us regarding the optimal definition of ''rapid progression.'' Such studies require serial follow-up of patients to calculate change in GFR over time, with more frequent measurements and longer duration of follow-up providing more accurate estimates. The Work Group reviewed cohort studies of the general population that have evaluated rapid progression of kidney function (Table 22 ).

Approaches to define decline in kidney function included absolute rate of loss 232, 233, 235 as well as percent change. 221, 234 tudies consistently demonstrate that a more rapid rate of loss of kidney function was associated with an increased risk of adverse clinical outcomes including death and vascular related events. These studies have been limited however by relatively few patients with GFR levelso60 ml/min/1.73 m 2 , few measurements of SCr, and relatively short duration of follow-up to obtain accurate estimates of the rate of decline in kidney function. The precision of the estimate of the slope depends on a number of factors including the number of measurements of kidney function, biological variability, measurement error, and duration of follow-up. In general at least three measures of kidney function are required to permit an estimate of slope. 1 None of these studies assessed the impact of albuminuria on rate of ''rapid decline'' in kidney function. However as noted in Recommendation 2.1.1, ] [238] Two of the largest prospective cohort studies have shown an approximate two-fold increase in the rate of decline in GFR in the presence of proteinuria. 219, 220 Further evidence regarding the potential adverse effects of albuminuria on outcomes has been reported among patients with diabetes. The AER is one of the best indicators of diabetic nephropathy risk in both type 1 and type 2 diabetes, and patients with microalbuminuria have been reported to have 200 to 400% higher risk for progression to proteinuria than patients with normal albuminuria. 239, 240 Long-term follow-up studies have also demonstrated the increased risk of ESRD associated with albuminuria among patients with both type 1 and type 2 diabetes. 241, 242 iven the recognized limitations in defining rapid progression, the Work Group aimed to provide options for determination of progression, based on their clinical utility, and ease of use. One approach included an assessment of change in GFR category, combined with a minimal percent change. A criterion requiring both a change in GFR category (e.g., change from G2 to G3a) and percent change would ensure that small changes GFR from 61 to 59 ml/min/1.73 m 2 for example, which represents a change in category but a minimal change in GFR, would not be misinterpreted to represent progression. A change of o25% in a pair of GFR estimates may reflect physiologic variation rather than true progression.

Additional work to inform this definition has been undertaken, using data from the Alberta Kidney Disease Network (AKDN). 243 In this analysis 598,397 adults with at least two out-patient measures of SCr spaced at least 6 months apart were included. Progression was defined as ''certain'' (rise or drop) if during the median follow-up time of 2.4 years there was a change in GFR category combined with a 25% or greater change in GFR from the baseline measurement (constituting a certain rise or a certain drop). Participants who changed GFR category but did not meet the criterion of 25% change in GFR were categorized as ''uncertain'' rise or drop. The reference group was comprised of participants who did not change GFR category over the follow-up period. As outlined in Table 23 , compared to participants with stable eGFR, those with a certain drop had an almost two-fold increase in the risk of all-cause mortality (HR 1.89; 95% CI 1.83-1.95) 244 and a five-fold increase in the risk of ESRD (HR 5.11; 95% CI 4.56-5.71). 245 Lesser degree of risk was present for those with an uncertain drop (reflecting a change in category only). It is worth noting that once progression occurs, the last eGFR which has a lower level often contains much of the information about risk of ESRD and extrapolation of progression using information from prior progression and the most recent eGFR is only useful if the information about progression is precise and the patient's trajectory is linear.

The second approach to define progression takes into account the rate of change in kidney function based on a slope analysis. In this approach the rate of loss is defined by both the absolute rate of change and the percent change, as determined among a cohort of 529,312 adults who had at least 3 outpatient SCr measurements over a four year period (AKDN databases). Two indices of change in eGFR were estimated: the absolute annual rate of change (categorized as: increase, stable and -1, -2, -3, -4, and Z -5 ml/min/1.73 m 2 / year decline); and the annual percentage change (categorized as: increase, stable, -1 to -2, -3 to -4, -5 to -6, and Z-7 percent decline/year). The adjusted ESRD risk associated with each category of change in eGFR was estimated, using stable eGFR (no change in eGFR) as the reference. The results were adjusted in two ways: for eGFR and covariates at the time of the first eGFR measurement, and at the time of the last eGFR measurement. As outlined in Table 24 , the risk of ESRD increased almost two-fold for every 1 ml/yr decline in eGFR, when adjusted for covariates and eGFR at the time of the first eGFR measurement. The risk remained significant, but was less pronounced, when adjustments were performed at the time of the last eGFR measurement. This suggests that extrapolation of kidney function beyond the last measurement of eGFR is still informative, but identifies a lesser risk. Similar results were obtained when change in eGFR was defined by a percentage. With respect to the impact of changes in albuminuria over time, a study from the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint trial (ONTAR-GET) investigators showed that a greater than or equal to twofold increase in albuminuria from baseline to 2 years associated with a nearly 50% higher mortality (HR 1.48; CI 1.32-1.66), while a greater than or equal to twofold decrease in albuminuria associated with 15% lower mortality (HR 0.85; CI 0.74-0.98) compared with those with lesser changes in albuminuria, after adjustment for baseline albuminuria, BP, and other potential confounders. Increases in albuminuria also significantly associated with renal outcomes, defined as ESRD or doubling of SCr (HR 1.40; CI 1.11-1.78), while a decrease in albuminuria was associated with a decrease of the combined renal outcome (HR 0.73; CI 0.57-0.95). 246 owever, preliminary analysis of cohort studies is limited and suggests that further research is required to more accurately determine the change in albuminuria associated with an increased risk of kidney disease progression.

There is accumulating evidence that the trajectories of GFR decline are non-linear, and may take a number of different courses over time. The longer an individual is followed over time, the more likely they are to experience non-linear change in trajectory. 247, 248 The non-linearity of a trajectory may be due to intercurrent illness, changes in medication, intrinsic to the disease process, or any combination of these factors. Li et al. 247 described individual GFR progression trajectories over twelve years of follow-up among participants in the African American Study of Kidney Disease (AASK) (Figure 18 ). The authors reported that 41.6% of patients exhibited a greater than 90% probability of having a non-linear trajectory; in 66.1% the probability of non-linearity was 450%.

Studies to date evaluating rapid progression of kidney disease have been limited to North American (White and African American), European, and Asian populations. Given the differences in the prevalence of CKD by ethnic group, there may also be variations in rate of progression by ethnicity, and in particular ethnic groups with high rates of comorbid conditions leading to ESRD such as the Aboriginal population. Thus, the definition of rapid progression may vary according to country or region. However, by using a general definition of progression, which includes change of category of eGFR or albuminuria or both, as well as a numeric change over an established period of time, we believe that the definition of progression can be used in all cohorts.

Practitioners should monitor the GFR and albuminuria at regular intervals to identify rates of decline which exceed that normally demonstrated. The rate of GFR decline may be relatively constant over time in an individual; however the rate of GFR decline is highly variable among people and over long periods of observation, within individuals. Thus clinicians are encouraged to evaluate changes in GFR or albuminuria in the context of multiple observations over time, and with attention to clinical events which may have impacted the change. A number of factors influence assessment of rate of progression including frequency and duration of GFR and albuminuria measurements as well as 247 ; accessed http://download.journals.elsevierhealth.com/pdfs/journals/0272-6386/PIIS0272638611017896.pdf factors related to the patient (e.g., baseline GFR, comorbidities, age etc.).

There are no implications for public policy at this time.

The practical issue in clinical practice and clinical trials is how to define progression (as inferring true deterioration in kidney function) with meaningful thresholds that are easy to understand for the non-nephrologist. While changes in proteinuria may signify change in clinical condition, there are no data yet to suggest that change in proteinuria is itself reliably associated with progression of CKD per se. This may be confusing to practitioners, since a change in quantity of proteinuria is an indication for referral.

We recommend research to confirm rates which can be classified as slow, moderate, and rapid progression of kidney disease. The rate to define ''rapid progression'' may vary depending on the outcome considered, such as kidney failure versus mortality for example. It will be important for researchers to determine methods by which reproducible classification systems for describing rates of progression can be developed. There are increasing data to suggest the nonlinearity of progressive disease in many individuals. This makes extrapolation risky and warrants continued assessment of the slope on a regular basis.

Small fluctuations in GFR are common and should not be misinterpreted to represent progressive decline in kidney function. Many factors can cause a small change in GFR including medications, volume status, measurement error, and biological variability. Assessment of progressive decline in GFR needs to take into account the number of measurements considered and time period of assessment.

In pediatrics, information about utilty of serial creatinine measurements over periods of time during which growth (and muscle mass increase) is occurring, for the diagnosis of progression or regression, remains problematic.

Applying strict GFR criteria in order to develop cutoff values associated with 'true' progression in terms of any one individual child is not currently possible. Conceptually the movement from various levels of renal function downward, in particular if that movement is associated with increasing comorbidities or intensity of such, is a reasonable approach.

The most informative data available in children comes from the longitudinal GFR data from CKiD. 72 Examination of the whole cohort reveals an annual decline in GFR of À4.2%; median GFR decline was À1.8 ml/min/1.73 m 2 (interquartile range [IQR] À6.6 to 1.6); this can be expressed as a median absolute decline in GFR of À4.3 ml/min/1.73 m 2 (IQR À11.9 to 1.1) and À1.5 ml/min/1.73 m 2 (IQR À5.0 to1.8).

Given that the lower IQR in each of the overall cohort and both sub-groups is equal to or exceeds the suggested decline of 5 ml/min/1.73 m 2 as stated here, we suggest that it is reasonable to adopt this definition at least for the purpose of classification as it relates to 'rapid' progression; note the above values all relate to measured GFR.

Increasing numbers of any given measurement of an event generally allow for greater precision and accuracy. However, the simple repeated measurements of creatinine over time are less likely to be valuable in children than in adults with CKD. Unlike adults with static muscle mass and hence expected stability in creatinine values, or adults with expected declining muscle mass and hence expectations of declining creatinine if renal function has remained stable, pediatric populations have a situation of increasing muscle mass with expectation of increasing creatinine in the otherwise normal child without CKD. In a child with CKD who is growing therefore, and in particular one going through puberty, the simple comparison of creatinine values over time will likely not be sufficient to presume CKD progression or regression has occurred. The two exceptions to this would be a) a series of creatinine measurements demonstrating significant increase over a short period of time wherein there is no demonstrable or expected gain of muscle mass; b) values of creatinine that over time demonstrate an increase to levels above that which is expected of the child's age and sex based on population normative value for the lab and method of measurement.

2.1.4: In people with CKD progression, as defined in

Recommendation 2.1.3, review current management, examine for reversible causes of progression, and consider referral to a specialist. (Not Graded)

This statement intends to reassure patients and practitioners that not all patients necessarily require referral to specialists, but that this should be considered in the event that the patient or clinician requires further guidance or prognostic information. CKD progression, contextualized for the individual circumstance, does not always require referral, and earlier guidelines may not have been so overt in stating this. Faster or unusual trajectories of progression should alert the patient and physician to assess for potentially reversible causes of progression.

Progressive kidney disease requires the need for more aggressive assessment and treatment, which may include referral to a nephrologist or specialist (if they are not currently being managed by a nephrologist).

Decline in GFR may not be constant, with acute decline superimposed on CKD (see Chapter 2.2 for discussion of factors associated with progression of a more chronic nature). ] [251] [252] Readers are also referred to the KDIGO Clinical Practice Guideline for Acute Kidney Injury 7 which contains additional relevant details regarding risk factors for rapid progression and management strategies.

Rapid sustained decline in GFR could also be considered an indication for referral once potentially reversible factors as outlined above have been assessed and treated. The principles guiding referral include additional input from a nephrologist into management of CKD and preparation for RRT, such as that which may be required with rapidly declining GFR. The NICE guidelines for CKD also recommend referral for ''rapidly declining GFR'' although the definition of rapidly declining is not provided. 186 Most studies assessing nephrology referral have focused on early versus late referral, and not considered the impact or implications of nephrology referral in situations associated with rapid decline in GFR. 253 The evidence that such referral will change outcomes is not clear but given that nephrologists often have access to education and specialized services, which are essential for optimal preparation for RRT, referral to a specialist is recommended. Additional discussion of when to consider a referral to a nephrologist can be found in Chapter 5.

Risk factors for acute deterioration in kidney function may vary slightly by country of origin, although the common categories in general (e.g., medications, volume depletion and urinary tract obstruction) would be relevant irrespective of country. This set of statements serves to ensure that attention to changes in kidney function in those identified with kidney disease is part of the usual care of these individuals.

Practitioners should be aware of the common risk factors for acute-on-chronic kidney disease resulting in a rapid loss of kidney function. Acute rapid deterioration in kidney function should alert the practitioner to assess for these potentially reversible causes of progression. This assessment would include an evaluation for potential urinary tract obstruction as well as a volume assessment and detailed medication review.

Readers are referred to the KDIGO Clinical Practice Guideline for Acute Kidney Injury 7 for a detailed discussion of issues related to definition, diagnosis, and treatment of rapid progression of kidney dysfunction, as defined by AKI.

There are no specific numeric values to define ''rapid loss'' as this varies within and between disease states, individuals, and populations. The key point for practitioners is to serially review individual trajectories of changes in kidney function so as to determine stability or not, identify changes in previous stable trajectories, and to be aware of the importance of circumstances where AKI changes the course of CKD. Further studies are required to determine the rate of loss of GFR that constitutes rapid loss of kidney function. In children, interpretation of serial changes in SCr requires understanding of normative value ranges and drivers of change in SCr which are different than in adults. As some of these risk factors are modifiable they should be actively identified and, if present, be treated as they may impact long-term outcomes including cardiovascular conditions, QOL, and progression of CKD.

It is not yet clear what the relative weight of each of these factors is in predicting in an individual whether he/she will have progressive CKD.

As progression of CKD is defined as either a progressive decrease in GFR or a progressive increase in albuminuria, we should consider separately whether different factors would predict these two components of CKD differently. Given the limited evidence, this will not be discussed separately. It is however clear that a subject with a lower GFR to start with will progress more rapidly to a GFR o15 ml/min/1.73 m 2 , just as a subject with already elevated albuminuria will progress more rapidly to an ACR 4300 mg/g (430 mg/ mmol). Similarly, it is well-known that a subject with membranous glomerulopathy is more likely to progress to nephrotic syndrome, while a subject with adult polycystic kidney disease is more likely to progress to ESRD.

Although there are many cross-sectional studies that describe factors associated with a low GFR and factors associated with a high albuminuria, the number of studies evaluating which factors are associated with progressive decreases in GFR and progressive increases in albuminuria are more limited. In general, it can be argued that most of the above-mentioned factors are associated with a more progressive rise in albuminuria and a more progressive fall in GFR. Most recently, studies have focused on the development of risk scores for identifying progressive decreases in GFR and progressive increases in albuminuria. It has not yet been established which prediction formula could best be used. Some formulas use just simple demographic and clinical measures, while others also include laboratory tests. Some were developed for high-risk populations, such as people with known underlying CVD, 254 with CKD in general, 255 or with specific causes of CKD, such as IgA nephropathy, 256 diabetic nephropathy, 257 or renal artery stenosis. 258 Others developed a risk prediction model in the general population. 259 This latter model included age, race, gender, and in dichotomized version, the presence of anemia, hypertension, diabetes, and CVD history. More recently, two studies used more accurate laboratory parameters in addition to demographic characteristics. The first study was in patients with an eGFR of 15-60 ml/min/1.73 m 2 /year, and included age, gender, eGFR, albuminuria, and serum calcium, phosphate, bicarbonate and albumin. 260 The second study was in subjects from the general population and included age, eGFR, albuminuria, measured levels of BP and C-reactive protein (CRP). 261 The results from these predictive models require validation in future studies but they demonstrate the potential and the capabilities of developing clinically meaningful classification of risk for individual patients. Further research is required to establish whether prediction formulas may differ for different ethnicities.

Studies describing factors associated with lower GFR and higher ACR have been described from all over the world. In general, there is much overlap between these data. It may be that in different parts of the world the relative weight of each of the factors predicting progressive increases in albuminuria or decreases in GFR may substantially differ.

Evidence Base

The evidence base for these statements is reviewed in the NKF KDOQI Clinical Practice Guideline for Diabetes and CKD: 2012 Update 293 and will not be reiterated in full here. It should be noted that the evidence that intensive glycemic control reduces the microvascular complications of diabetes is based almost exclusively on prevention of development of albuminuria (ACR 430 mg/g or 43 mg/mmol) and prevention of increasing albuminuria. Evidence from the three most recent studies, Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation (ADVANCE), 294 Action to Control Cardiovascular Risk in Diabetes (ACCORD), 295 and the Veterans Affairs Diabetes Trial (VADT), 296 is summarized in Table 25 . ADVANCE, ACCORD, or VADT did not show significant benefits of more intensive glycemic control on creatininebased estimates of GFR. However, in the Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications (EDIC) follow-up study, 1.4% of participants in the previously intensive treatment group and 3.6% of those in the previously conventional treatment group developed SCr concentrations 42.0 mg/dl (177 mmol/l) (P ¼ 0.01) and 0.6% versus 1.9% required kidney replacement therapy (P o0.03). 297 For patients with type 2 diabetes, intensive treatment in the United Kingdom Prospective Diabetes Study (UKPDS) was associated with a 67% risk reduction for a doubling of plasma creatinine levels at 9 years (0.71% of the intensive group and 1.76% of the conventional group, P ¼ 0.027). 298

International Relevance

The incidence and prevalence of diabetes is rising around the world and at rapid rates in developing countries. Glycemic control is therefore one of the most important strategies for delaying progression of CKD, irrespective of region or country. It is recognized that not all hypoglycemic strategies or treatments are available in all countries.

Implications for Clinical Practice and Public Policy

Practitioners should encourage glycemic control in all people with CKD and diabetes, including referral to education sessions and diabetic clinics where available. Public health policies and diabetic strategies should include screening in high-risk populations such as those with diabetes, as the presence of CKD would confer higher risk of adverse events, and could represent an opportunity for intensified intervention with large implications for health-care.

Areas of Controversy, Confusion, or Non-consensus

Recommendations on the use of specific medications for glycemic control (e.g., metformin and glyburide) remain variable depending on different perspectives. These are covered more fully in Chapter 4 on medication dosing and AKI.

Clarification of Issues and Key Points

Glycemic control improves outcomes in people with diabetes, with or without CKD. Those with diabetes and CKD have higher risk of adverse outcomes and therefore presumed higher benefit from control. Many agents are renally excreted and therefore adjustments to doses may be necessary as GFR declines or if patients are acutely unwell (see Chapter 4 on medication dosing).

Caveats in measuring glycemic control with HbA 1C

HbA 1C may not be reflective of glucose control in people with CKD who have reduced red cell life span, and thus should be interpreted with caution. Review of blood sugar daily logs may be more reliable.

Clinicians should be aware that HbA 1C measurements that inform glycemic control are based on an assumed red cell life span of 90 days. In people with CKD the RBC life span is shortened, even if receiving erythropoiesis-stimulating agents (ESAs). As such, measurement may only reflect glycemic control over a shorter time period than the presumed 3 months and thus, HbA 1C measurements may be falsely low. 0] [301] [302] [303] [304] Ongoing research intitiatives comparing HbA 1C with glycated albumin using continuous glucose monitoring suggest that glycated albumin may provide a more reliable index of glycemic control in people with advanced CKD.

Pediatric Considerations

It is recommended that the Guidelines of the American Diabetes Association 305 or similar national guidelines for diabetes management in children and adolescents, be reviewed to address issues related to management of diabetic children either with, or at risk of, CKD.

Salt intake

3.1.19:

We recommend lowering salt intake to o90 mmol (o2 g) per day of sodium (corresponding to 5 g of sodium chloride) in adults, unless contraindicated (see rationale). (1C) 3.1.19.1: We recommend restriction of sodium intake for children with CKD who have hypertension (systolic and/or diastolic blood pressure 495 th percentile) or prehypertension (systolic and/or diastolic blood pressure 490 th percentile and o95 th percentile), following the age-based Recommended Daily Intake. (1C) 3.1.19.2: We recommend supplemental free water and sodium supplements for children with CKD and polyuria to avoid chronic intravascular depletion and to promote optimal growth. (1C)

RATIONALE

In subjects with CKD, impaired excretion of sodium is often present. High sodium intake increases BP and proteinuria, induces glomerular hyperfiltration and blunts the response to RAAS blockade. Lowering salt intake not only reduces BP, but also lowers albuminuria. The importance of salt intake in the general management of CKD patients cannot be overemphasized, hence the need for specific statements here.

We appreciate that there are some conditions in which salt 295 6.3% (45 mmol/mol) versus 7.6% (60 mmol/mol) 21% k in new ACR 3-30 mg/mmol (30-300 mg/g) 32% k in ACR progression to 430 mg/mmol (4300 mg/g) VADT 296 6.9% ( restriction may be harmful, and hence the qualifier ''unless contraindicated.' These conditions include salt losing nephropathies and those prone to hypotension and volume contraction who do not have heart failure.

A systematic review of 16 studies addressing salt intake and kidney disease set out to establish whether variations in dietary sodium consumption influence renal outcomes in people with CKD. 306 Despite marked heterogeneity, the review suggested that increased salt intake was associated with worsening albuminuria and an increased likelihood of reduction of GFR. Although the quality of the studies included was insufficient to support the authors' hypothesis that increased salt intake is nephrotoxic, the results were strong enough to suggest modest dietary avoidance of salt should be encouraged in people with CKD, especially those with hypertension and/or proteinuria. In a randomized, double-blind, placebo-controlled trial of salt reduction in 40 Afro-Caribbean hypertensives, a salt-restricted diet (approximately 5 g daily) significantly reduced 24-hour urinary protein excretion by 19% and led to a fall in systolic and diastolic BP of 8 mm Hg and 3 mm Hg, respectively. 307 The fall in urinary protein excretion correlated with a reduction in urinary sodium excretion, not with BP reduction. Individuals with metabolic syndrome may be especially sensitive to the effects of sodium intake. Hoffman and Cubeddu examined the role of salt intake in increased BP in 109 subjects with metabolic syndrome. 308 Salt restriction from an average usual intake of 8.2 g/day to nearly 2.3 g/day reduced the percentage of hypertensive patients from 23.8% to 8.2%. In a six-month prospective controlled trial, 110 patients with GFR categories G4 or G5 (GFRo30 ml/min/ 1.73 m 2 ) followed a low-sodium (circa 1 g/day) diet as part of either a LPD (0.6 g/kg/day) or very low-protein diet (VLPD) supplemented with essential amino acids (0.35g/kg/day), or a free diet. 309 BP fell significantly in the VLPD group from 143±19/84±10 to 128±16/78±7 mm Hg (Po0.0001), despite reduction of antihypertensive drugs. The improved BP correlated with decreased urinary sodium and the authors concluded that the antihypertensive effect was due to reduction of salt intake independent of actual protein intake. Finally, a randomized controlled crossover trial in 52 nondiabetic subjects with CKD compared the effects of a lowsodium diet (target 50 mmol [1.15 g] sodium per day) versus a regular sodium diet (target 200 mmol [4.60 g] sodium per day) on lowering of proteinuria through RAAS blockade. 310 he reduction of proteinuria by the addition of a low-sodium diet to angiotensin-converting enzyme inhibition was significantly larger (Po0.001) than the addition of angiotensin receptor blockade to angiotensin-converting enzyme inhibition and similarly the reduction of systolic BP by the addition of a low-sodium diet was significantly larger (P ¼ 0.003) than the addition of angiotensin receptor blockade. The authors concluded that sodium restriction to a level recommended in guidelines was more effective than dual renin-angiotensin blockade for reduction of proteinuria and BP in non-diabetic nephropathy.

Salt intake has been identified as an important driver of high BP in all countries and in adults, thus this recommendation is of international relevance and applicability. The relevance and caveats to children in different situations around the world merits further review.

In most developed countries, a reduction in salt intake can be achieved by a gradual and sustained reduction in the amount of salt added to foods by the food industry. In other countries where most of the salt consumed comes from salt added during cooking or from sauces, a public health campaign is needed to encourage consumers to use less salt. The range of sodium intake associated with improved long-term outcomes is easily achievable and may have the potential to greatly improve health outcomes in patients with CKD around the world.

While salt restriction is of benefit on a population-basis, and in most people with hypertension and CKD, there may be individual conditions in which salt restriction might be detrimental (e.g., those with salt wasting tubular disorders; those either hypotensive in the absence of heart failure or those prone to volume contraction). Thus while this general statement applies to the majority of people, individualization is required based on clinical circumstance. This may be particularly relevant to children.

The suggested relative salt restrictions for children with CKD and/or hypertension are age-based with consideration given to both average intakes and upper limit values. The recommended upper limit for sodium intake from which a reduced intake could be derived is provided in Table 26 . It must also be recognized that children with CKD often have underlying tubular conditions that predispose to numerous electrolyte losses, including sodium. For these children a supplemental rather than restricted sodium intake will be required. Hyperuricemia is common in people with CKD and is defined by urate concentrations above 7.0 mg/dl (420 mmol/l) as measured by automated enzymatic (uricase) laboratory methods. Concentrations obtained with colorimetric methods are approximately 1 mg/dl (60 mmol/l) lower. The Work Group believe it important to acknowledge the accumulating body of evidence describing the association of hyperuricemia with CKD and adverse cardiovascular outcomes, and thus list hyperuricemia as a potential contributor to progression. However, at the time of current writing, there is not a reliable body of evidence from which to recommend treatment of hyperuricemia for the specific goal of delaying progression of CKD. Thus, the wording of this ungraded statement is very deliberate.

Observational data had implicated uric acid in the progression of CKD suggesting that adverse outcomes in people with CKD may be improved by specific uric acid lowering therapy. Small studies using appropriate RCT design have shown reduced left ventricular mass, improved endothelial function, and reduced progression of CKD in people with either symptomatic or asymptomatic hyperuricemia and CKD. Thus, the specific statement is intended to ensure and foster RCTs to properly assess the risk and benefits of uric acid lowering strategies in people with CKD.

1] [332] Exercise may reduce cardiovascular risk through its beneficial effects on BP, triglycerides, high-density lipoprotein cholesterol (HDL-C), insulin resistance, and glycemic control. 4] [335] [336] [337] [338] [339] Less data are available on the beneficial effects of exercise on early CKD. However, as cardiovascular risk gradually increases with both a lower GFR and a higher ACR, it is expected that exercise will also help to prevent progressive CVD in less severe CKD. Indeed, in subjects with GFR categories G3a-G4 (GFR 15-59 ml/min/ 1.73 m 2 ), long-term exercise training improved physical impairment, arterial stiffness, and health-related QOL. 340 It has therefore been argued that exercise training is imperative in CKD patients 341 and that support programs including selfmonitoring, verbal reinforcement, and motivation should be applied [342] [343] [344] in an attempt to prevent the high cardiovascular risk in CKD. A prospective study compared the benefits of 6 months of regular walking in 40 predialysis patients with GFR categories G4-G5 (GFRo30 ml/min/1.73 m 2 ) (20 in an exercising group and 20 patients who continued with usual physical activity for comparison). Improvements noted after 1 month were sustained to 6 months in the 18 of 20 who completed the exercise study. These included improvements in exercise tolerance (reduced exertion to achieve the same activity), weight loss, improved cardiovascular reactivity, avoiding an increase in BP medication and improvements in quality of health and life and uremic symptom scores as assessed by questionnaire. 345 n the absence of diabetes, hypertension or other cardiovascular risk factors there has been a lack of evidence to support a causal link between obesity and CKD. 7] [348] The evidence in population studies is conflicting; some studies have failed to link obesity with decreased GFR, 349, 350 possibly because BMI in isolation is a poor measure, while others suggest that CKD is independently associated with BMI. 351 It has been known for some time that obesity is associated with secondary focal and segmental glomerulosclerosis, 352 yet significant associations between obesity and CKD in large observational studies such as The Framingham Heart Study disappear after adjustment for age, gender, and cardiovascular risk factors. 353 However, systematic review and meta-analysis of weight loss interventions in CKD have shown weight loss to be associated with significant decrease in proteinuria and systolic BP with no further decrease in GFR in people with CKD during a mean follow-up of 7.4 months. 354 A further systematic review drew very similar conclusions. Weight loss interventions were associated with decreased proteinuria and albuminuria by 1.7 g (95% CI 0.7-2.6 g) and 14 mg (95% CI 11-17 mg), respectively (Po0.05). 355 Each 1-kg weight loss was associated with 110 mg (95% CI 60-160 mg; Po0.001) decrease in proteinuria and 1.1 mg (95% CI 0.5-2.4 mg; P ¼ 0.011) decrease in albuminuria, respectively, independent of reduction in BP.

Multiple studies document a clear association between smoking and renal damage in the general population, patients with diabetes, and hypertensive patients. 356 [363] [364] [365]

Exercise, weight loss and smoking cessation in CKD are equally important in all countries and thus this recommendation is of international relevance and applicability.

Implementation of this recommendation has no public health cost but has the potential to make far-reaching public health gains both in terms of population health and healthcare economics.

RATIONALE International Relevance

The importance of lifestyle recommendations and dietary counseling cannot be overstated. It is however recognized that within the context of different countries, health-care systems and jurisdictions, the degree to which these can be implemented is variable. These recommendations serve as a 'best practice' suggestion.

3.2 COMPLICATIONS ASSOCIATED WITH LOSS OF KIDNEY FUNCTION

People with CKD are prone to develop a variety of complications which reflect loss of endocrine or exocrine function of the kidneys. The incidence and prevalence of these complications increase with severity of CKD as defined predominantly by GFR categories (Table 27 ).

It is beyond the scope of this guideline to describe each of the complications and the proposed treatment options for them in detail as guidance for these conditions can be found in other documents. However, for the purpose of completeness, the key complications and management recommendations for people with CKD are addressed in this section.

In addition to these complications, we have described strategies to delay progression of CKD which are in part predicated on the identification and management of the clinical, metabolic, and hematologic complications. Note that not all people with CKD will have all of the complications and complications may not occur at the same rate or to the same degree in individuals with the same categories of GFR or albuminuria. Nonetheless knowledge of the common complications and treatment options is important in the care of CKD.

Management of Complications

Anemia in CKD. Anemia is an important complication of CKD because it contributes significantly to the heavy symptom burden of CKD. It has a major impact on the lives of people with CKD but it is potentially reversible with appropriate treatment. The guideline statements included here are those we consider to be the key considerations for people with non-dialysis CKD. Interested readers are referred to the KDIGO Clinical Practice Guideline for Anemia in CKD 11 for comprehensive guidance on this topic.

These statements reflect the need to measure Hb in people with CKD in order to detect if anemia is present, given its association with poor outcomes and its use in prediction models. Anemia is a common occurrence in CKD patients, though variable in its time of presentation and severity within individuals. Thus, the guidelines stress that evaluation and treatment of anemia in people CKD should be undertaken as in other individuals, and emphasize that anemia due to CKD is a diagnosis of exclusion. Furthermore, the guidelines stress that laboratory values used for diagnosis do not imply therapeutic thresholds or targets. For details, consult KDIGO Clinical Practice Guideline for Anemia in CKD. 11 idence Base

Conventionally anemia is defined as a Hb concentration lower than the established cutoff defined by the WHO. 368 ifferent biological groups have different cutoff Hb values below which anemia is said to be present, ranging from 11 g/dl (110 g/l) for pregnant women and for children between 6 months and 5 years of age, to 12 g/dl (120 g/l) for non-pregnant women, and to 13 g/dl (130 g/l) for men (Table 28 ).

Globally the prevalence of anemia is 24.8% of the population, much of this is linked to nutritional deficiency exacerbated by infectious disease. However, altitude, race, and smoking will each also have an impact on Hb concentration. Hb concentration can be expected to increase by about 0.6 g/dl (6 g/l) in women and 0.9 g/dl (9 g/l) in men for each 1000 m of altitude above sea level. 369 ] [372] Smoking is associated with elevated carboxyhemoglobin levels, which are associated with a compensatory increase in total Hb concentration. Hence, the US Centers for Disease Control and Prevention have recommended a downwards adjustment of 0.3 g/dl (3 g/l) for smokers. 373 Thus, specific Hb levels expected for different levels of eGFR should be contextualized within the normal distribution of the population.

The recommended thresholds for diagnosis and evaluation of anemia should not be interpreted as being thresholds for treatment of anemia but simply for the identification of this complication. Practice preferences with respect to treatment strategies should be directed according to local resources.

3.2.3:

K when clinically indicated in people with GFR Z60 ml/min/1.73 m 2 (GFR categories G1-G2); K at least annually in people with GFR 30-59 ml/ min/1.73 m 2 (GFR categories G3a-G3b);

K at least twice per year in people with GFR o30 ml/min/1.73 m 2 (GFR categories G4-G5).

5] [376] The exact frequency of monitoring of Hb concentration will be influenced by kidney function, underlying disease process, the initial Hb concentration, and the rate of change in Hb concentration. The latter will also be influenced by whether or not anemia is being treated and what type of treatment is undertaken. The statements specifically address the need to measure Hb concentrations at a minimum and are not intended to deter the clinician from more frequent measurements as required for individual circumstances.

The initial evaluation of anemia in CKD is geared towards the exclusion of causes other than those directly related to kidney disease (relative iron and erythropoietin deficiency); see KDIGO Clinical Practice Guideline for Anemia in CKD 11 for details.

Anemia as defined above is found in people with CKD in increasing proportions as GFR declines (Table 27 ). This is due to a number of reasons, including loss of erythropoietic hormone efficacy, production, substrate deficiency (most notably iron), and other conditions which may contribute to the lack of effective erythropoiesis. For a full description of the evidence behind this statement please refer to the KDIGO Clinical Practice Guideline for Anemia in CKD. 11

Frequency of Hb concentration monitoring and the initial evaluation of anemia should not differ by country, except that causes of anemia other than those related to CKD do differ. Nutritional deficiencies in resource-poor areas are common, particularly iron deficiency, which is frequently exacerbated by infectious diseases.

Anemia is associated with increased morbidity, mortality, and consumption of health-care resources. The major health consequences include poor pregnancy outcome, impaired physical and cognitive development, increased risk of morbidity in children, and reduced work productivity in adults.

Treatment of anemia in CKD. The last 30 years have seen a major transition in approach to the treatment of anemia in people with CKD beginning with the introduction of erythropoietin therapy into clinical practice and the subsequent resurgence of interest in iron therapies. The promise of early intervention with anemia treatment in non-dialysis CKD suggested by observational study has been tempered with the reality of risks of adverse cardiovascular outcomes in RCTs. Nevertheless treatment of anemia with iron and ESAs has an important positive role to play in the lives of people with CKD. For the treatment of anemia in people with CKD, we suggest clinicians refer to the KDIGO Clinical Practice Guideline for Anemia in CKD for further details. 11 he key points for practitioners to remember include the following:

1. Work-up for anemia in CKD should include assessment of secondary causes including iron deficiency. 2. Iron replacement is often effective in anemia of CKD as initial therapy and routes of administration (intravenous or oral) will be determined by clinicians, patient preferences, and local available resources. 3. ESA therapy is not recommended in those with active malignancy, or recent history of malignancy. 4. In most people with CKD, ESAs should not be used to intentionally increase the Hb concentration above 11.5 g/dl (115 g/l) 5. For pediatric patients, the selection of Hb concentration at which ESA therapy is initiated should be individualized after taking into account the potential benefits (e.g., improvement in QOL, school attendance/performance, and avoidance of transfusion) and potential harms.

3.3 CKD METABOLIC BONE DISEASE INCLUDING LABORATORY ABNORMALITIES

Changes in bone mineral metabolism and alterations in calcium and phosphate homeostasis occur early in the course of CKD and progress as kidney function declines (Table 27 ). These changes are grouped under the umbrella term Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) which includes renal osteodystrophy and extraskeletal (vascular) calcification related to abnormalities of bone mineral metabolism.

Renal osteodystrophy is the component of CKD-MBD that is identified and quantified through bone biopsy histomorphometry and includes osteitis fibrosa (hyperparathyroidism), osteomalacia, and adynamic bone disease. The evidence on which existing recommended guideline treatment targets for serum concentrations of calcium, phosphate, and parathyroid hormone (PTH), and the strategies to achieve these targets, is exclusively observational and thus problematic for that reason. Furthermore, very little of the evidence is derived from patients with non-dialysis CKD. Nevertheless we feel it is important to include here some of the key statements relating to mineral metabolism abnormalities in patients with non-dialysis CKD from the KDIGO Clinical Practice Guideline for the Diagnosis, Evaluation, Prevention, and Treatment of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) published in 2009. 9 These statements will be qualified where new data since the publication of the CKD-MBD guidance have become available. , the subsequent frequency of testing will be determined on an individual basis by the actual value and any intervention that may be introduced.

The importance of examining combinations of parameters of mineral metabolism is likely to be no different in patients with less severe CKD, but this has not been tested in non-dialysis populations.

There are also racial differences in the parameters of mineral metabolism. In a multicenter cohort of 227 black and 1633 non-black patients with early CKD, blacks had similar 1,25(OH) 2 D levels compared with non-blacks but significantly lower levels of 25(OH)D with higher levels of calcium, phosphate, and PTH, and were significantly more likely to have hyperphosphatemia than non-blacks. 380 In multivariable analyses adjusted for age, gender, eGFR, BMI, and diabetes, blacks had significantly lower 25(OH)D and higher PTH levels than non-blacks. Examining the relationships between 25(OH)D and PTH in 8415 adult participants (25% black and 24% Mexican-American) in NHANES 2003-2004 and 2005-2006, and the relationship between 25(OH)D and bone mineral density (BMD) in 4206 adult participants (24% black and 24% Mexican-American) in the 2003-2004 NHANES sample, Guitierrez et al. found significant racial differences. 381 Blacks and Mexican-Americans had significantly lower 25(OH)D and higher PTH concentrations than whites (Po0.01 for both). Bone mineral density significantly decreased (Po0.01) as serum 25(OH)D and calcium intake declined among whites and Mexican-Americans, but not among blacks (P ¼ 0.2).

The association between black race and Hispanics and secondary hyperparathyroidism, independent of known risk factors, suggests that novel mechanisms may contribute to secondary hyperparathyroidism in non-whites with CKD. Testing for these parameters would therefore be informed by the demographics of the population. In different countries and regions, the ability to measure these parameters may c h a p t e r 3 vary, thus the authors of the guideline statements appreciate that implementation of regular measurements of all these parameters may not be possible in all jurisdictions.

Given there remains no clear recommendation as to 'expected' values in CKD nor consensus on thresholds regarding treatment, the testing of PTH, and vitamin D parameters would lead to substantial costs to the health-care system. Abnormal values lead to repeat testing. There are no data to suggest how effective or useful repeated monitoring of abnormal values is, nor what an acceptable interval of monitoring should be to inform care. Laboratory testing for phosphate and calcium is relatively inexpensive, but treatment and ongoing monitoring may be expensive. At the current time, recommendations for testing frequency may be problematic for clinical practice.

The inter-relationship of calcium, phosphate, and PTH, and the potential impact of vitamin D on these mineral metabolites and extraskeletal calcification remains an area of research and debate among clinicians. Newer research examining the role of FGF-23, an important molecule in phosphate, PTH, and vitamin D homeostasis, has caused many to question the previous focus on PTH values as misplaced. The questions of whether vitamin D therapies are toxic in some or all patients and what values of phosphate are pathologic have yet to be resolved.

Application of guidelines related to bone health, growth, and CKD in children is extremely complex. Numerous issues arise, including age-related variation in normative values, comparisons across age, sex, size, and the need to account for pubertal changes etc., when one considers the options and targets for evaluation and treatment.

It is recommended that in the application of any of these specific guidelines, the reader carefully reviews the publications as they relate to pediatrics, starting with the following two documents and then accessing the most currently available pediatric CKD resources for the topic(s).

Recommended primary pediatric CKD-MBD resources:

K KDOQI Clinical

While there is an appreciation that BMD is measured in many elderly, this statement is intended to highlight for the clinician the fact that the information gained from BMD in those with reduced GFR may be false, leading to either under-or over-treatment. Although fractures rates and fracture-related mortality are elevated in CKD, bone densitometry does not reliably predict fracture risk in patients with GFR o45 ml/min/1.73 m 2 and neither does it predict the type of renal osteodystrophy. Thus, BMD measurements do not provide the information usually sought from such testing, which is usually the basis of interventions.

Decreased bone mass and changes in bone microarchitecture occur early in CKD and worsen with progression of disease such that patients with CKD are at increased risk of bone fracture. 383 Bone strength is determined by the density and quality of the bone. Dual-energy x-ray absorptiometry (DXA) scanning measures density of bone but is not able to determine bone quality (cortical and trabecular microarchitecture). Studies using high-resolution peripheral quantitative computed tomography (HR-pQCT) demonstrate abnormalities in the cortical and trabecular microarchitecture of patients with early CKD compared with healthy control subjects. 384 Although abnormalities of both DXA and HR-pQCT associate with fractures in patients with CKD, receiver operator characteristic curve analysis suggests that neither technique is predictive of fracture (area under the curve o0.75), although this improved for patients with longer duration of CKD. 385 In a cross-sectional study, the combination of these imaging techniques with markers of bone turnover improved prediction of fracture. 386

A major component of fracture risk is related to fall risk, thus reduction in fall risk may be achieved through establishment of falls prevention programs. Such programs include medication review; prevention of postural hypotension; cardiac pacing, where appropriate; home hazard assessment and modifications; muscle strengthening and retraining; and treatment of vitamin D deficiency.

The combination of measurements of bone thickness, BMD of femoral neck, and a history of fracture may be useful to identify CKD patients who might benefit from fracture prevention strategies. Prospective studies are needed to assess the utility of these parameters for fracture prediction in the CKD population.

Systematic review of serum concentrations of calcium, phosphate, and PTH and the risk of death and CVD in people with CKD showed that the risk of death increased 18% for every 1 mg/dl (0.33 mmol/l) increase in serum phosphate concentration (RR 1.18; 95% CI 1.12-1.25). 387 here was no association seen with either PTH or serum calcium and all-cause mortality (Figure 19 ). Of the 327,644 subjects included in the review only 16,247 were not receiving dialysis and of these only 8990 were people with GFR o60 ml/min/1.73 m 2 not receiving RRT. In these subjects the risk of all-cause mortality for each 1 mg/dl (0.33 mmol/l) increase in serum phosphate concentration was very similar (RR 1.29; 95% CI 1.12-1.48). As with all subjects included there was no evidence of an association between serum calcium concentration and all-cause mortality in people with CKD not receiving RRT (RR 1.02; 95% CI 0.81-1.29). Data for associations of calcium, phosphate, and PTH with cardiovascular death were only available in one of the studies included.

In the Multi-Ethnic Study of Atherosclerosis (MESA) study, the associations of serum phosphate concentrations with vascular and valvular calcification were examined in 439 people with GFR o60 ml/min/1.73 m 2 . Each 1 mg/dl (0.33 mmol/l) increase in serum phosphate concentration was associated with a 21% (P ¼ 0.002), 33% (P ¼ 0.001), 25% (P ¼ 0.16), and 62% (P ¼ 0.007) greater prevalence of coronary artery, thoracic, aortic valve, and mitral valve calcification, respectively. 388 The strength of the associations did not differ by age, race, or diabetes. Adjustment for serum concentrations of PTH and 1,25(OH) 2 D did not alter the strength of the associations.

Factors affecting gastrointestinal phosphate absorption include 1,25(OH) 2 D, food content, phosphate bioavailability and phosphate binders (natural and prescribed). Sources of dietary phosphate are protein-rich foods, including dairy products, meat, and fish as well as legumes, nuts, chocolates and inorganic phosphate additives such as those found in carbonated drinks. In a non-vegetarian Western diet, over half the dietary intake of phosphate comes from animal protein. Although the phosphate content of plant-derived phosphate is higher than animal derived, its bioavailability in terms of gastrointestinal absorption is lower. 389 Inorganic phosphate additives have the highest bioavailability. A number of clinical studies detail benefit from dietary phosphate and protein control in terms of secondary hyperparathyroidism and progression of CKD in people with moderate CKD. 390 Few studies have evaluated the impact of dietary phosphate restriction on bone disease or vascular calcification and only one has addressed survival. In people on hemodialysis, a post hoc analysis suggested that more restrictive prescribed dietary phosphate was associated with poorer indices of nutritional status and a greater need for nutritional supplementation. 391 There was a stepwise trend toward greater survival with more liberal phosphate prescription, which reached statistical significance among subjects prescribed 1001 to 2000 mg/d and those with no specified phosphate restriction, raising concerns about protein energy malnutrition with dietary phosphate restriction. The means used to achieve phosphate restriction may therefore be important.

Table 29 details the relative cost comparisons of phosphate binders currently in clinical use for which there is observational or study trial data demonstrating their efficacy. Data concerning comparative patient-level outcomes such as mortality are not available.

There are a number of agents available for phosphate binding which are listed in the table ranked in order of relative cost, appreciating that both availability and specific costs are country-and era-specific.

A Cochrane meta-analysis considered 60 RCTs or quasi-RCTs (7631 participants) that assessed the effects of various phosphate binders in adults with CKD. 392 The authors concluded that all available phosphate-binders reduced serum phosphate concentrations in comparison to placebo but that data to date do not support superiority of novel non-calcium binding agents for patient-level outcomes such as all-cause mortality and cardiovascular end points in CKD.

Availability of different phosphate binders differs around the globe. Thus, recommendations as to specific agents are not possible within the context of these statements. Similarly, dietary phosphate intake may be different around the world, c h a p t e r 3 rendering this problem of greater or lesser significance in different jurisdictions. Measurement of specific hormones (PTH, vitamin D) is expensive and may not inform care sufficiently to warrant the expense at this time.

Existing data support prevention of hyperphosphatemia and associated secondary hyperparathyroidism in CKD. In the absence of hypercalcemia, there is no indication to prescribe phosphate-binders that are less cost-effective than calcium-based agents. Current data are insufficient to make recommendations about target levels of serum calcium or PTH concentrations that should be achieved in order to reduce mortality or cardiovascular morbidity in people with CKD not requiring dialysis. Assay variability of PTH and vitamin D remains problematic and this issue is beyond the scope of this document. The practitioner and health-care administrators are advised to appreciate this problem in developing targets for care or thresholds for treatment.

As per comments above, the data to support levels of laboratory values for interventions, types of interventions, and target values remain problematic. Thus recommendations for therapy remain similarly problematic and practice varies depending on location and resource availability. Likely correlation of symptoms with blood values and addressing laboratory abnormalities within that context is a pragmatic approach at the current time. The non-specialist is asked to seek advice from local experts for best advice for specific individuals.

The KDIGO guidelines on this subject have not been updated at the time of the writing of this CKD guideline.

2] [313] [314] [315] Reduction of SUA by allopurinol has been reported to delay progression of CKD in people with both diabetic and nondiabetic CKD. 316, 317 Treatment of asymptomatic hyperuricemia has also been reported to improve kidney function even in subjects with normal levels of GFR. 318, 319 Both GFR and endothelial function significantly improved in asymptomatic hyperuricemic subjects randomly assigned to 300 mg/day of allopurinol in comparison to placebo. 318 A separate doubleblind, placebo-controlled, parallel-group study in 67 people with CKD (GFR 30-60 ml/min/1.73 m 2 ) and left ventricular hypertrophy (LVH) randomly assigned subjects to treatment with allopurinol (300 mg/day) or placebo for 9 months. 320 n comparison to placebo, the allopurinol-treated subjects had significant reductions in left ventricular mass assessed by magnetic resonance imaging (MRI), and improvements in endothelial function assessed by flow-mediated dilation of the brachial artery and in central arterial stiffness assessed by pulse-wave analysis. Another study randomized 70 subjects with known hyperuricemia or SUA concentra-tions Z7.0 mg/dl (Z420 mmol/l) to treatment with either allopurinol monotherapy (100-200 mg/day) or a combination of allopurinol and a citrate preparation (3 g/day). 321 UA concentrations were decreased in both groups but to a significantly lower level by combination treatment. GFR assessed by CrCl increased in the combination therapy group but remained unchanged in those treated with allopurinol alone. Other uric acid lowering agents have also been reported to improve outcomes in people with CKD. In an 8-week, placebo-controlled group comparison of rasburicase and placebo, a single 4.5 mg dose of rasburicase significantly lowered SUA and resulted in a significant improvement in kidney function assessed by CrCl. 322 In a post hoc analysis of 1342 patients with type 2 diabetes mellitus and nephropathy participating in the Reduction of Endpoints in Non-Insulin-Dependent Diabetes Mellitus with the Angiotensin II Antagonist Losartan (RENAAL) trial, Miao et al. examined the relationship between change in SUA concentration after 6 months of treatment with losartan and doubling of SCr or ESRD. 323 Baseline SUA was 6.7 mg/dl (400 mmol/l) in placebo and losartan-treated subjects. During the first 6 months, losartan lowered SUA by 0.16 mg/dl (9.5 mmol/l) [95% CI 0.30-0.01; P ¼ 0.031] as compared with placebo. The risk of doubling of SCr or ESRD was decreased by 6% (95% CI 10%-3%) per 0.5-mg/dl (30-mmol/l) decrement in SUA during the first 6 months. This effect was independent of other risk markers, including albuminuria.

There are no data to support or refute the importance of hyperuricemia in different geographical reasons or ethnic groups. Further study is needed.

There is insufficient evidence to recommend the use of uric acid lowering agents in asymptomatic individuals for the specific purpose of delaying CKD progression. Further large trials are required to better understand the potential benefit of uric acid lowering for this purpose. Lifestyle 3.1.21: We recommend that people with CKD be encouraged to undertake physical activity compatible with cardiovascular health and tolerance (aiming for at least 30 minutes 5 times per week), achieve a healthy weight (BMI 20 to 25, according to country specific demographics), and stop smoking. (1D)

People with CKD have self-reported reduced physical functioning and are not as aerobically fit as the general population. Frailty, impaired physical performance, disability, and geriatric syndromes are common among older adults even with mild kidney disease. Reduced physical functioning and inactivity are associated with increased mortality and poor QOL. Obesity is associated with increased morbidity, mortality, and reduction in life expectancy and leads to an increase in the incidence of diabetes, hypertension, and dyslipidemia. Associations between smoking and CKD suggest that smoking increases the risk of kidney failure and that smoking cessation decreases that risk. Thus, this statement reflects the importance of ensuring lifestyle recommendations.

It is important to realize that some factors predicting progression of CKD are modifiable. This holds true for lifestyle measures such as cessation of smoking and prevention of obesity. It also subtends to lowering of BP, lowering of albuminuria and prevention of hyperglycemia. A further factor that may be modifiable is the underlying cause of CKD. As various causes may respond to targeted treatment, finding the cause of CKD is the starting point of the work-up of a subject with CKD. If this causal disease is modifiable, for example by immunosuppressive treatment, then such treatment is the first step to consider. Management of patients with CKD and delay of progression are dealt with in Chapter 3 and more fully in other guidelines (see KDIGO Clinical Practice Guideline for Glomerulonephritis 8 and KDOQI Clinical Practice Guideline for Diabetes and CKD: 2012 Update. 262 )

While there are prediction equations available using combinations of eGFR, albuminuria, cause of CKD, and some or all of the laboratory abnormalities listed, they have not been used in clinical practice to guide therapy as yet. Furthermore, while the associated abnormalities clearly increase in severity with worsening kidney function, normalizing them in some instances has not changed progression to ESRD. The need for prediction equations to take into account changes over time (trajectories) and stability or instability of specific factors has been raised by many. Nonetheless, the ability to determine progression versus stability should be of value for patients and clinicians.

Clinicians should attempt to determine stability or progression of patients with CKD for the purposes of informing care. Further research is required to determine which formula best predicts who will have progressive increases in albuminuria and progressive decreases in GFR. The key components of prediction equations for ESRD may well be different than prediction equations for cardiovascular events or death.

A more complete discussion of the evidence in children supporting these factors as potentially related to risk of progression, in addition to the pediatric specific risk of growth/puberty, can be found in the Pediatric Considerations for Recommendation 1.3.1.

DELAYING PROGRESSION OF CKD

The following section describes key recommendations and guidance for people with CKD with respect to delaying progression of CKD. General lifestyle recommendations are provided as well as caveats given for those with diabetes. Cardiovascular risk reduction including management of hypertension, dyslipidemia, and hyperuricemia is further addressed. Unless otherwise stated, the guidance is intended to apply to adults with CKD.

For the practicing clinician, ideally working with a team of health-care professionals, it is important to institute general lifestyle modification practices in people with CKD so that they may gain the benefit of these in addition to more kidney-specific strategies. Often these general measures are overlooked or disregarded in people with CKD, thus their utility is underscored here.

3.1 PREVENTION OF CKD PROGRESSION

The management of progression of CKD is aimed at addressing a multiplicity of factors known to be associated with progression. There are general measures which have been shown to address cardiovascular health and CKD together, or each separately. Addressing CVD risk factors may indirectly and directly impact CKD progression. Strategies include general lifestyle measures which improve cardiovascular health, BP control, and interruption of the RAAS. In addition, control of other metabolic parameters such as blood sugar, uric acid, acidosis, and dyslipidemia may also be important. This section deals with management of BP, RAAS interruption, glycemic control and dietary/lifestyle manipulations which have been examined in the context of delaying progression of CKD.

BP and RAAS interruption

The following statements are excerpted and where necessary, condensed, from the KDIGO Clinical Practice Guideline for the Management of Blood Pressure in CKD. 10 3.1.1: Individualize BP targets and agents according to age, coexistent cardiovascular disease and other comorbidities, risk of progression of CKD, presence or absence of retinopathy (in CKD patients with diabetes), and tolerance of treatment as described in the KDIGO 2012 Blood Pressure Guideline. (Not Graded) These statements are worded to maintain consistency with the KDIGO Clinical Practice Guideline for the Management of Blood Pressure in CKD, 10 where the full rationale and evidence behind the statements may be found. In detailing BP targets, we recognize that we have not made recommendations or suggestions concerning lower limits of BP. The risks of overtreatment should be specifically considered when making decisions about BP lowering and this is encapsulated in the first two guideline statements.

CKD and risk of AKI 3.1.12: We recommend that all people with CKD are considered to be at increased risk of AKI. (1A) 3.1.12.1: In people with CKD, the recommendations detailed in the KDIGO AKI Guideline should be followed for management of those at risk of AKI during intercurrent illness, or when undergoing investigation and procedures that are likely to increase the risk of AKI. (Not Graded)

Observational data suggest a strong association between preexisting CKD and AKI. The appreciation that CKD patients may be more susceptible to AKI is the purpose of the above set of statements. However, methodological issues such as how CKD and AKI are defined in clinical studies and the statistical adjustments for non-uniformity of comorbidities among various studies may affect the validity of observed associations. These statements would be applicable in pediatrics, though the data are not available for this specific issue.

CKD is designated as a risk factor for AKI because of the epidemiological association between the two. 263, 264 6] [267] [268] [269] [270] [271] CKD is a potent predictor of acute decline in kidney function following exposure to radiocontrast, 272 major surgery, 273 and other medical conditions. 274 su et al. 14 compared the pre-hospitalization MDRD GFR of 1764 adult members of the Kaiser Permanente Northern California health-care system who developed dialysis-requiring AKI during hospitalization with 600,820 individuals who did not. Compared with a reference baseline GFR of Z60 ml/ min/1.73 m 2 , a baseline GFR of 45-59 ml/min/1.73 m 2 was associated with an adjusted odds ratio (OR) of in-hospital AKI of 1.66 (95% CI 1.40-1.97). For GFR values of 15-29 ml/ min/1.73 m 2 , the adjusted OR for in-hospital AKI was 20.42 (95% CI 17. 40-23.96). The presence of diabetes, hypertension, and proteinuria increased the likelihood of developing in-hospital AKI, with adjusted OR of 1.99 (95% CI 1.78-2.23), 1.55 (95% CI 1.37-1.76) and 2.84 (95% CI 2.52-3.19), respectively. The authors concluded that CKD is the main risk factor for AKI during hospitalization. A contrasting approach by Singh et al. defined AKI as dialysisrequiring acute renal failure. 275 Because the clinical decision to dialyze a patient is frequently influenced by a higher overall SCr, presence of hemodialysis access, or consideration of inevitable progression to ESRD, this definition of AKI could bias toward capturing more AKI cases in CKD patients. Moreover, in patients with advanced CKD, the progression of CKD to ESRD may sometimes be difficult to separate from acute-on-chronic renal failure. A cohort study by Lafrance et al. followed a referred CKD population in British Columbia for a median of 19.4 months after achieving a GFR of r30 ml/min/1.73 m 2 . Forty-five percent had at least one episode of AKI. 276 In another cohort study of 920,985 adults in Alberta, Canada with at least one outpatient measurement of SCr and proteinuria and not requiring chronic dialysis, risk of admission with AKI increased with heavier proteinuria and reduced GFR. 16

The incidence of AKI in CKD populations may be different around the world, or have different etiologies. It is not yet clear what the recovery rates from AKI are in the CKD population, and how these vary around the world dependent on cause and duration of AKI.

Interpretation of published data examining the influence of pre-existing CKD on the increased likelihood of AKI is potentially confounded by a number of issues. These include the comorbidities associated with CKD, influenced by repeated exposure to various nephrotoxic insults or in-hospital errors, 57, 277 or primarily due to the altered physiology in CKD. There are also methodological issues such as how CKD and AKI are defined in clinical studies and the varying statistical adjustments for comorbidities.

A further important issue to clarify is whether pre-existing CKD influences the outcome of AKI. Currently, there is no single biomarker that can differentiate 'acute' from 'chronic' kidney disease and help to address this issue. 9] [280] [281] [282] [283] Data from the Program to Improve Care in Acute Renal Disease (PICARD) reveal lower in-patient mortality and median length of stay in intensive-care unit (ICU) subjects with acute-on-chronic renal injury compared with non-CKD subjects with AKI, though the post-discharge dialysis rates were higher in subjects with pre-existing CKD. 284

AKI is relatively common in CKD populations and impacts progression adversely. Clinicans should attempt to minimize avoidable episodes of AKI (see Chapter 4 for more details) as part of a holistic approach to delaying progression.

RESEARCH RECOMMENDATIONS

Prospectively designed clinical studies with a clear and uniform definition of CKD and AKI and adjusted for comorbidities are needed to determine the: K frequency of AKI events in a CKD population; K outcome of AKI in patients with CKD; K importance of proteinuria in addition to low GFR in the risk of AKI.

Protein intake

These statements are worded to reflect the potential benefits and dangers of varying dietary protein intake (DPI) in people with CKD. Excess dietary protein leads to the accumulation of uremic toxins, conversely insufficient protein intake may lead to loss of lean body mass, and malnutrition (the latter more frequent in the elderly). The benefits of dietary protein restriction include reduction of accumulation of metabolic waste products that may suppress the appetite and stimulate muscle protein wasting. The role of dietary protein restriction in slowing progression of CKD is more controversial and advanced CKD is associated with a protein wasting syndrome which is directly correlated with morbidity and mortality.

Note that statements about reduction in dietary protein do not apply to pediatric populations given issues related to growth and nutrition.

6] [287] [288] [289] Pedrini et al. 288 compared a low-protein diet (LPD), defined as a DPI of 0.4 to 0.6 g/kg/day, with a usual diet (5 RCTs, N ¼ 1413) over a period of follow-up ranging between 18-36 months in people with non-diabetic CKD and GFR o55 ml/min/1.73 m 2 . Fouque et al. 285 updated this analysis to include 8 RCTs in people with non-diabetic CKD (N ¼ 1524). DPI in their low-protein group was between 0.3-0.6 g/kg/day and follow-up ranged from 12-24 months (5 of 8 studies were in people with GFR categories G4-G5 (GFR o30 ml/min/ 1.73 m 2 ). Roberston et al. 289 compared diabetic subjects (8 studies in type 1 diabetes, N ¼ 322; 1 study in type 2 diabetes, N ¼ 263). DPI in the low-protein subjects was 0.3-0.8 g/kg/day and usual protein intake ranged from 1-2 g/kg/day. Mean follow-up ranged from 4.5 months to 4 years. In all studies, compliance with a low DPI was poor. There was no convincing or conclusive evidence that long-term protein restriction delayed the progression of CKD. The largest RCT to date was the MDRD Study. 227 The MDRD Study compared the effects of LPD and BP control on the progression of CKD in over 800 subjects split into 2 groups. Study A compared a DPI of 1.3 g/kg/day (usual protein intake) with 0.58 g/kg/day (LPD) in 585 subjects with a measured GFR of 25-55 ml/min/1.73 m 2 and the actual DPIs were 1.11 and 0.73 g/kg/day, respectively. Study B randomized 255 patients with a measured GFR 13-24 ml/ min/1.73 m 2 to DPIs of 0.58 g/kg/day (LPD) or 0.28 g/kg/day supplemented by keto-aminoacids (denoted by VLPD-KA), actual DPIs were 0.69 and 0.46 g/kg/day, respectively. In each of the randomization groups ACE-Is were allowed and were used by 32-44% of patients. Mean follow-up was 2.2 years and the loss of GFR was estimated by the slope of 125 I-iothalamate clearance measured over 2 years. There was no difference in GFR decline between groups in Study A and in Study B. Although there was a somewhat faster decline in GFR in the LPD group compared with the VLPD-KA group, this was not significant.

A follow-up study of the original MDRD Study followed those subjects recruited to Study B between 1989-1993 up until the year 2000. Median duration of follow-up until kidney failure, death, or administrative censoring was 3.2 years and median time to death was 10.6 years. 290 The authors concluded that assignment to a very LPD did not delay progression to kidney failure, but appeared to increase the risk of death in the long-term. The chief limitation of this follow-up study was the lack of measurements of DPI and nutritional measurements during the course of the long-term follow-up period and it is therefore not known how many patients continued with the LPD or the VLPD-KA diets after the study concluded.

There is some evidence to suggest that higher protein diets above the recommended daily intake may accelerate renal functional decline in people with early CKD. In a study of 1624 women enrolled in the Nurses 0 Health Study, Knight et al. described the effect of protein intake over an 11-year period in women with eGFR Z80 ml/min/1.73 m 2 (normal renal function) at baseline and those with eGFR 55-80 ml/min/1.73 m 2 . 291 DPI was measured twice during the study period at intervals of 4 years using a semiquantitative food-frequency questionnaire that inquired about the average intake of specified foods and beverages during the previous year. In women with normal renal function at baseline high protein intake was not significantly associated with change in eGFR. However in those with eGFR 55-80 ml/min/1.73 m 2 at baseline, protein intake was significantly associated with a change in eGFR of À1.69 ml/min per 1.73 m 2 (95% CI, À2.93 to À0.45 ml/ min per 1.73 m 2 ) per 10 g increase in protein intake. The effect was greatest in those with the highest intake of non-dairy animal protein.

Dietary protein restriction of o0.80 g/kg/day appears to offer no advantage and any dietary protein restriction should include careful monitoring of clinical and biochemical markers of nutritional deficiencies. A high total protein intake, particularly high intake of non-dairy animal protein, may accelerate renal function decline in people with CKD and should be avoided.

Studies on protein restriction have not been widely tested in different ethnicities or within cultures with low baseline proten intake or purely vegetarian diets. Thus, the applicability of statements to all regions of the world is limited.

Clinicians should be aware of different sources of protein, and if lowering of protein is recommended, education and monitoring for malnutrition should be implemented. Appropriate dietary counseling for CKD patients may have healthcare resource implications, although as part of a combined strategy to manage obesity, salt intake, and diabetes may be considered cost-effective on a population basis in certain countries. Avoidance of malnutrition is important.

Data are mixed on the value of protein restriction, the values which are achievable in general populations, and the level of GFR at which they should be instituted. Nonetheless, the Work Group felt that on balance there is enough data to support a reduction in dietary protein in selected individuals. It is important to avoid this advice in those with evidence of or at risk of malnutrition.

A Cochrane review addresses this issue in children 292 by examining two RCTs with a total of 250 children to determine the effect of protein restriction on a number of variables. The RR of progression to ESRD in the low-protein restricted versus normal group was 1.12 (95% CI 0.54-2.33). At two years, progression of kidney disease was not significant as measured by change in CrCl: mean difference 1.47 ml/min/1.73 m 2 (95% CI À1. 19-4.14) or growth as measured by mean weight difference: À0.13 kg (95% CI À1.10-0.84) or mean height difference: À1.99 cm (95% CI À4.84-0.86). The conclusion of the authors was that a lowprotein diet did not delay progression to kidney failure in children, but it may be detrimental to growth.

Glycemic control

Diabetes is the leading cause of CKD worldwide. Diabetic nephropathy occurs in 25-40% of patients with type 1 or type 2 diabetes within 20-25 years of disease onset and is an independent risk factor for early death due to CVD. The mortality rate in people with diabetes and urinary ACR 430 mg/g (43 mg/mmol) is more than twice that in those with normal urinary albumin levels.

The National Kidney Foundation (NKF) KDOQI Clinical Practice Guideline for Diabetes and CKD 293

These statements are included to reflect the current evidence that achieving a hemoglobin A 1c (HbA 1c ) level of B7.0% (53 mmol/mol) is able to prevent the microvascular complications of diabetes, although recognizing that the major risk for patients attaining HbA 1c levels o7.0% (o53 mmol/mol) is hypoglycemia, and that this risk will be higher in people with lower levels of kidney function.

There is a substantial amount of data to support 25(OH)D deficiency in general and CKD populations 367, 393 which is likely multifactorial. In addition to 25(OH)D deficiency, note has been made that there is a progressive increase in prevalence of 1,25(OH) 2 D deficiency with lower GFR category, which occurs earlier than 25(OH)D deficiency (Figure 20 ).

No relationship between 25(OH)D levels and 1,25(OH) 2 D levels was apparent but there was a strong association between 1,25(OH) 2 D deficiency and PTH concentration. Of particular note, a higher urinary ACR was associated with lower levels of 1,25(OH) 2 D at GFR values of o60 ml/min/ 1.73 m 2 . The potential importance of these deficiencies has been illustrated in a number of studies examining the relationship between low levels of 25(OH)D and 1,25(OH) 2 D and all-cause and cardiovascular mortality in a different cohorts. 393, 394 espite the associations with mortality, systematic review of published data to date on vitamin D supplementation in patients with CKD not on dialysis has only shown an improvement in biochemical end points. A series of publications 395, 396 have attempted to summarize the efficacy of vitamin D therapy on biochemical, bone, cardiovascular, and mortality outcomes in people with CKD and not requiring dialysis. No formulation, route, or schedule of vitamin D compound was found to alter the mortality risk or need for dialysis although vitamin D compounds significantly lowered serum PTH concentrations. None of the studies assessed reported outcomes related to CVD, bone disease, or mortality.

The importance of vitamin D deficiency has been addressed in both general and CKD populations. Specific populations have been identified as more likely to be vitamin D deficient depending on cultural and environmental factors; estimates of worldwide prevalence of vitamin D deficiency range from 25-60%. CKD populations within high-risk areas may be particularly vulnerable. The interplay between loss of kidney function and exacerbation of vitamin D deficiency is not known.

Vitamin D supplementation improves biochemical end points similar to active vitamin D analogs with a lower burden of costs and side effects. Measurement of serum 25(OH)D is expensive and in the CKD population with vitamin D deficiency, simple vitamin D replenishment is all that is indicated until new evidence becomes available. Except for education or research purposes, there is no need to measure vitamin D levels in general practice.

The appropriate dose and formulation of vitamin D, target range for treatment, frequency, route of administration, and safety at different severities of CKD remain to be determined.

3.3.6:

We suggest not to prescribe bisphosphonate treatment in people with GFR o30 ml/min/1.73 m 2 (GFR categories G4-G5) without a strong clinical rationale. (2B)

The risk-benefit ratio of bisphosphonates has not been well studied in CKD populations. Indications for bisphosphonate therapy include osteoporosis, corticosteroid therapy, malignant disease and Paget's disease. In people with CKD and GFR categories 460 ml/min/1.73 m 2 with osteoporosis and/ or at high risk of fractures, and in people with GFRs between 30-60 ml/min/1.73 m 2 with normal PTH, osteoporosis and/or at high risk of fracture, treatment should be the same as for the general population (although dose modification may be necessary, see Table 30 ).

In people with CKD at lower categories of GFR (o30-35 ml/min/1.73 m 2 ), the correct diagnosis of osteoporosis becomes increasingly complex and other forms of renal osteodystrophy requiring alternative management strategies to osteoporosis require exclusion before treatment with bisphosphonates is considered. In people with adynamic renal bone disease, more likely at lower GFR categories, there is a lack of evidence of either harm or benefit of bisphosphonates on bone strength or vascular calcification.

Bisphosphonates increase BMD, reduce bone turnover, and reduce the risk of fragility fractures. The bioavailability of intravenous bisphosphonate formulations is 100% but the bioavailability of oral formulations is only 1-5%. Approximately 50-80% of available bisphosphonate is taken up by bone and the remaining 20-50% is excreted in urine without being metabolized. Although oral bisphosphonates have not been shown to adversely affect kidney function in people with GFRs as low as 15 ml/min/1.73 m 2 , in post hoc analysis of clinical trial data their safety and efficacy below GFRs of 30 ml/min/1.73 m 2 have not been well-validated and intravenous bisphosphonates have been implicated in nephrotoxicity, especially when rapidly infused (Table 30 ). 9, 397, 398 Thus, from a patient's safety perspective, the statement serves to limit exposure of those with abnormal kidney function to these agents.

Given cost and clinical practice variation, the use of bisphosphonates varies around the world. Thus, this statement may be less applicable in different jurisdictions. Given the widespread use of bisphosphonates in developed countries, especially in older women who are also likely to have some degree of kidney dysfunction, the cessation of bisphosphonates in that group may be problematic. There is a need to monitor clinical practice and understand the implications of this recommendation for large populations, who may or may not be deriving benefit from these agents.

Despite these concerns, primary care data from the USA suggest that prescription of bisphosphonates is common in people with CKD. Even in the subset with GFR o30 ml/min/1.73 m 2 , bisphosphonate use was no less prevalent than in the non-CKD population. 399 People with CKD in this study were nearly seven times more likely to receive a bisphosphonate than active vitamin D. Similar uncertainty about the efficacy and safety of such treatment for people with CKD was demonstrated in a study of people under the care of a UK renal unit. 400 Half of all people prescribed bisphosphonates had a GFR o30 ml/min/ 1.73 m 2 and yet 50% of people with higher GFRs and documented osteoporosis were not prescribed bisphosphonates.

Further study is required to elucidate whether or not bisphosphonates, through reduction of bone turnover in people with pre-existing low bone turnover states, would be beneficial or harmful both for bone and vascular calcification.

3.4 ACIDOSIS

The prevalence and severity of metabolic acidosis in people with CKD progressively rises as GFR falls (Table 27 ).

Adaptations in acid excretion by the kidneys initially prevent a fall in serum bicarbonate concentration but as GFR continues to decline below 40 ml/min/1.73 m 2 , metabolic acidosis commonly develops.

2] [403] [404] [405] [406] [407] [408] [409] [410] The suggestion that treatment of acidosis may be beneficial was first made by Richard Bright, 411 later Cr-EDTA GFR 46.2 ± 6.0 ml/min/1.73 m 2 ) and proteinuria (3.2 ± 0.8 g/24 hours). 414 They suggested that oral sodium bicarbonate may protect the proximal renal tubule and help delay kidney disease progression. Mathur et al. randomized 40 subjects with mild to moderate CKD to oral bicarbonate (1.2 mEq/kg of body weight) or placebo for 3 months and suggested that correction of metabolic acidosis significantly attenuates the rise in blood urea. 415 A larger study randomly assigned 134 adults with moderate to severe CKD (CrCl 15 to 30 ml/min/1.73 m 2 ) and serum bicarbonate 16 to 20 mmol/l to either supplementation with oral sodium bicarbonate (1.82 ± 0.80 g/day) or standard care for 2 years. 416 Primary end points were rate of kidney function decline, the proportion of subjects with rapid decline of kidney function (43 ml/min/1.73 m 2 /yr), and ESRD (CrCl o10 ml/min [o0.17 ml/s]). Secondary end points were DPI, normalized protein nitrogen appearance, serum albumin, and mid-arm muscle circumference. Serum bicarbonate increased significantly in the bicarbonate group but despite the associated sodium load there was no difference in BP control, prescription of antihypertensives and loop diuretics, or hospitalization for heart failure compared with the control group. The decline in CrCl was significantly slowed in the bicarbonate group compared with controls (5.93 versus 1.88 ml/min/1.73 m 2 , Po0.0001), rapid progression was less prevalent (9 versus 45%, RR 0.15; 95% CI 0.06-0.40; Po0.0001), and fewer subjects developed ESRD (6.5 versus 33%, RR 0.13; 95% CI 0.04-0.40; Po0.001). Nutritional parameters also improved significantly with bicarbonate supplementation. In a non-randomized study the effects of supplementation of 1 mmol of bicarbonate equivalent per kg body weight per day for 2 years using oral sodium citrate in 30 subjects with hypertensive nephropathy was compared with 29 control subjects. 417 There were no statistically significant differences in baseline demographic data, systolic BP, venous bicarbonate levels, or parameters of kidney function between the two groups. All subjects were receiving angiotensin-converting enzyme inhibition throughout the study and BP was controlled to similar levels in both groups in a 6-month run-in period prior start of study. In those treated with oral sodium citrate, urine endothelin-1 excretion and N-acetyl-b-D glucosaminidase were each significantly lower while the rate of GFR decline was significantly slower after 24 months of treatment compared to the control group.

Alkali supplementation appears to be a promising low-cost, high-benefit adjunct treatment for patients with CKD and may be accessible to all populations. It is not known how prevalent acidosis is among different communities or countries around the world.

The use of sodium bicarbonate or calcium carbonate as a source of alkali should not present financial hardships in most practices or jurisdictions.

A potential concern regarding treatment of patients with CKD with sodium bicarbonate or sodium citrate is the possible associated sodium loading. A crossover study of 200 mmol/day (17 g/day) of sodium bicarbonate versus 200 mmol/day (12 g/day) of sodium chloride in 10 subjects with severe CKD (CrCl 2.5-16.8 ml/min [0.04-0.28 ml/s]) on an extremely low-sodium diet showed that sodium chloride but not sodium bicarbonate produced an increase in weight and BP. 418 A subsequent follow-up study suggested that if dietary sodium chloride intakes are near maximum tolerance, then sodium bicarbonate supplementation should be accompanied by reductions in sodium chloride intake to maintain sodium balance. 419 Given the lack of large and long-term trials, many are still not convinced that this is a reasonable recommendation, and is thus controversial. We would like to ensure that individual clinicians are aware of the controversy rather than making no statement at all.

DISCLAIMER

While every effort is made by the publishers, editorial board, and ISN to see that no inaccurate or misleading data, opinion or statement appears in this Journal, they wish to make it clear that the data and opinions appearing in the articles and advertisements herein are the responsibility of the contributor, copyright holder, or advertiser concerned. Accordingly, the publishers and the ISN, the editorial board and their respective employers, office and agents accept no liability whatsoever for the consequences of any such inaccurate or misleading data, opinion or statement. While every effort is made to ensure that drug doses and other quantities are presented accurately, readers are advised that new methods and techniques involving drug usage, and described within this Journal, should only be followed in conjunction with the drug manufacturer's own published literature. This section addresses a series of important topics which impact the outcomes of people with CKD. Specifically CVD, interpretation of tests for CVD, infections, vaccinations and hospitalizations, medications, and patient safety are addressed. This section is designed to help the practitioner appreciate the specific nuances related to testing and drug administration in people with CKD and to alert all clinicians to the fact that many common tests may not be as useful in people with CKD to diagnose or evaluate therapies. It was beyond the scope of the guideline and evidence review to thoroughly evaluate all tests with respect to sensitivity and specificity in different groups of people with CKD but future research may consider this as a useful direction.

4.1 CKD and CVD

Population-based studies have demonstrated an increased risk of death and cardiovascular mortality as GFR falls below 60 ml/min/1.73 m 2 or when albumin is detected on urinalysis. This is not explained by an increase in traditional risk factors. There are CKD-specific risk factors associated with more advanced CKD which drive the high rates of mortality and morbidity even at young ages. People with CKD are more likely to experience a cardiovascular event than to progress to ESRD, have a worse prognosis with higher mortality after acute myocardial infarction (MI), and have a higher risk of recurrent MI, heart failure and sudden cardiac death. Management of modifiable cardiovascular risk factors, such as improved BP and diabetes control, also reduces CKD progression.

4.1.1:

We recommend that all people with CKD be considered at increased risk for cardiovascular disease. (1A)

This statement is worded in this way to reflect the strong and independent associations between GFR and albuminuria categories and risk of CVD in people with CKD and applies to both adult and pediatric populations.

Large cohort studies have demonstrated the strong and independent associations between CVD (acute coronary syndrome

[ACS], stroke, heart failure and sudden cardiac death) and CKD by category of eGFR, after adjusting for known CVD risk factors, history of CVD events, and proteinuria. In those with an eGFR of 45-59 ml/min/1.73 m 2 , risk is increased by 43% and in those with eGFR below 15 ml/min/1.73 m 2 , risk is increased by 343%. 58 Although people with GFR category G5 (GFRo15 ml/min/1.73 m 2 ) are at the highest risk of a CVD event, there will be more events in people with GFR categories G3a-G3b (GFR 30-59 ml/min/1.73 m 2 ) because of the much higher prevalence at these categories. 420 These events occur at a younger age in people with CKD suggesting that CKD promotes CVD at an accelerated rate. 421 The prognosis after an acute event is related to level of GFR with a significant rise in mortality when eGFR falls below 45 ml/min/1.73 ] [424] Albuminuria is associated with duration and severity of hypertension; an adverse lipid profile with higher levels of total cholesterol, triglycerides and lipoprotein(a) and low HDL-C levels; 425 and abnormalities of coagulation. The presence of higher levels of proteinuria increases the risk of mortality and MI independently of level of eGFR. 426 Many studies have demonstrated low levels of urinary albumin to be associated with the increased risk of CVD in people with diabetes independent of renal function; however population studies of non-diabetic individuals have confirmed that even small amounts of albuminuria are associated with increased CVD risk. In the Third Copenhagen study, in people with microalbuminuria, risk of coronary heart disease was increased independently of age, sex, renal function, diabetes, hypertension, and plasma lipids. 427 The Chronic Kidney Disease Prognosis Consortium demonstrated that in general practice cohorts there was an increase in cardiovascular mortality when ACR is higher than 30 mg/g (3 mg/mmol). 4 nalysis of data from the Heart Outcomes Prevention Evaluation (HOPE) study demonstrated that any degree of albuminuria is a risk factor for cardiovascular events in individuals with or without diabetes. 428 The lack of a threshold of albuminuria for cardiac risk was also confirmed in the HUNT 2 Study 429 and the Losartan Intervention For Endpoint Reduction in Hypertension (LIFE) study in patients with LVH. 430 Albuminuria and low eGFR were synergistic cardiovascular mortality risk factors in the HUNT 2 study and using both ACR and eGFR improved cardiovascular risk stratification at all age levels, but particularly in persons 70 years and over. 429 n the MDRD Study cohort of patients with GFR categories G3a-G4 (GFR 15-59 ml/min/1.73 m 2 ), cystatin C level was strongly associated with all-cause and cardiovascular mortality particularly in the elderly. 431 Analysis of data from MESA and the Cardiovascular Health Study (CHS) demonstrated that the worst prognosis of CVD, heart failure, and progressive CKD was found in those subjects with CKD diagnosed using the cystatin C-based equation. 432 VH is common with CKD, is known to reflect target organ damage, and is associated with increased cardiovascular mortality in CKD. 360 It is also important to consider the role of CKD-specific risk factors particularly in patients with more severe CKD (GFR o30 ml/min/1.73 m 2 ) and correct them where possible. Anemia has been thought to have a particular role in the early development of CVD in people with CKD. Although treatment of anemia is associated with improved well-being and greater exercise capacity, the results of several RCTs of anemia correction have suggested that complete correction of anemia is not advisable in people with lower GFR (o60 ml/min/1.73 m 2 ). A meta-analysis of 9 RCTs comparing different target Hb levels suggests an increase in mortality and worse BP control with the higher treatment targets, independent of the GFR category. 433, 434 Those patients with LVH at baseline, a sign of target organ damage and which was present in 47% of the Cardiovascular Risk Reduction by Early Anemia Treatment with Epoetin Beta Trial (CREATE) cohort, had significantly worse cardiovascular outcomes when treated to the higher targets. 435 bnormalities of mineral metabolism with low 1,25dihydroxyvitamin D and PTH were found to occur early in CKD in the Study for the Evaluation of Early Kidney disease [SEEK] study, however serum calcium and phosphate were usually normal until eGFR fell below 40 ml/min/1.73 m 2 . 367 n association between elevated serum phosphate and cardiovascular mortality was demonstrated in a prospective study of people with CKD and this was also thought to be associated with low vitamin D levels. 436

While the majority of data for, and evidence of, the high risk of cardiovascular morbidity and mortality in the pediatric renal population stems from the ESRD (dialysis and transplant) populations, [437] [438] [439] [440] there is recognition that many if not all of the factors responsible for such outcomes will develop much earlier in this course of CKD. In fact, the current American Heart Association's guidelines for reduction of cardiovascular risk in pediatrics stratified the child with CKD to the highest risk category. 441 ased on data from the CKiD trial, Wilson et al. 442 demonstrated extremely high prevalence rates for four traditional cardiovascular risk factors (hypertension, dyslipidemia, abnormal glucose metabolism, and obesity) in a subgroup of this cohort of 586 children with iohexol GFR proven mild to moderate CKD. In this cross-sectional analysis of 250 children who had data on all variables of interest, median GFR of 45.2 ml/min/1.73 m 2 (IQR 34.6-58.2), the prevalence of hypertension was 46%, dyslipidemia was 44%, abnormal glucose metabolism was present in 21%, and obesity in 15%. Hypertriglyceridemia was common, seen in 33%. In aggregate, only 26% of the cohort had no risk factors present, 39% had at least one and 22% had two, 11% had three and 2% had all four risk factors present. The prevalence of all these factors remained elevated even when the population was restricted to those defined as lean, BMI o85 th . In this group, the presence of 2 or 3 cardiovascular risk factors was still seen in 20% and 2%, respectively. Within the lean group 12% demonstrated abnormal glucose metabolism. Finally, multivariate regression analysis of their data demonstrated that glomerular disease as a cause of CKD and the presence of nephrotic range proteinuria were associated with much higher odds of having cardiovascular risk factors, 1.96 (95% CI 1.04-3.72) and 2.04 (95% CI 0.94-4.43), respectively.

It is also well-recognized that carotid intimal media thickness and pulse wave velocity changes, as potential surrogate measures for vascular damage in children, can be increased in in children with CKD. 443, 444 or further detailed discussions of the pathophysiology and complexity of CVD in the pediatric CKD population, two recent review papers from Mitsnefes 445 and Shroff et al. 446 are suggested. Both papers identify and discuss the pathophysiology of both traditional and CKDspecific cardiovascular risk factors as seen in this population.

4.1.2:

We recommend that the level of care for ischemic heart disease offered to people with CKD should not be prejudiced by their CKD. (1A) 4.1.3: We suggest that adults with CKD at risk for atherosclerotic events be offered treatment with antiplatelet agents unless there is an increased bleeding risk that needs to be balanced against the possible cardiovascular benefits. (2B)

These statements are worded in this way to reflect the growing body of evidence that suggests that treatment of traditional risk factors in CKD patients is of benefit, and that attempts to modify or preclude usual investigations and therapies are not necessary in CKD patients. Inasmuch as CKD populations have been understudied, but likely inadvertently included in larger population studies, the rationale for risk factor modification is similar to that in the general population. The maintenance of cardiovascular health ultimately impacts 'kidney health' given the links between cardiac function, renal perfusion, atherosclerosis, and glomerulosclerois. The details of this complex biology are beyond the scope of these guidelines, but can be found in key references below.

There is evidence in the general population that smoking cessation is associated with a reduction in cardiovascular risk. In CKD there is evidence that smoking is associated with progression of renal disease, though no specific data exist that support cessation of smoking and delay of progression. 447 eople with CKD have reduced levels of muscle strength and aerobic activity. In those not on dialysis, exercise training is shown to improve functional capacity and BP. 448 eight loss in obese CKD patients can reduce rate of decline, proteinuria, and BP. 354 he Study of Heart and Renal Protection (SHARP) 449 is the largest RCT in people with CKD to date. The results demonstrate that a lipid-lowering strategy which included fixed dose simvastatin and ezetimibe resulted in a 17% reduction in atherosclerotic events, as compared to placebo. The cohort enrolled included those with eGFR under 60 ml/ min/1.73 m 2 , age greater than 40 years, and was an international study including more than 9000 subjects from around the globe. The lipid-lowering strategy was effective and safe. Lipid targets have not been established specifically for people with CKD. Treatment strategies should be implemented in accordance with current recommendations for high-risk populations.

At the time of this writing, the KDIGO Clinical Practice Guideline for Lipid Management in Chronic Kidney Disease was under preparation for public review. In brief, the key aspects of the draft recommendations include treating those at high risk for atherosclerotic disease with lipid-lowering therapies, regardless of LDL levels, in those 50 years of age and above. Since this Guideline has not yet been finalized, interested readers should refer to the final document when it is formally released in 2013.

The benefits of aspirin in people with CKD and hypertension was demonstrated in a post hoc analysis of the Hypertension Optimal Treatment (HOT) trial. 450 Jardine et al. reported that among every 1000 persons with eGFR o45 ml/min/1.73 m 2 treated for 3.8 years, 76 major cardiovascular events and 54 all-cause deaths will be prevented while 27 excess major bleeds will occur. They concluded that an increased risk of major bleeding appears to be outweighed by the substantial benefits. Clopidogrel is used as an alternative to aspirin but CKD has been shown to be associated with an increase in platelet reactivity and there is resistance to clopidogrel in people with CKD, diabetes, and CVD. 451 The Clopidogrel for Reduction of Events During Observation (CREDO) trial concluded that clopidogrel in mild or moderate CKD may not have the same beneficial effect as it does in people without CKD. Subjects with normal renal function who received 1 year of clopidogrel had a marked reduction in death, MI, or stroke compared with those who received placebo (10.4% versus 4.4%, P o0.001), whereas those with mild and moderate CKD did not have a significant difference in outcomes with clopidogrel therapy versus placebo (mild: 12.8% versus 10.3%, P ¼ 0.30; moderate: 13.1% versus 17.8%, P ¼ 0.24). Clopidogrel use was associated with an increased RR of major or minor bleeding, but this increased risk was not different based on renal function. 452

Although it is clear and mentioned in many guidelines that CKD is associated with an increase in CVD risk, it is not included in many assessment tools and there is a deficiency in ethnicity and regional specific tools.

The assessment tool from US Third Report of the National Cholesterol Education Program (NCEP III) does not include CKD. The Fourth Joint Task Force of the European Society of Cardiology suggest that both an eGFR of less than 60 ml/ min/1.73 m 2 and albuminuria increase risk but do not quantify the risk or include CKD in their Systematic COronary Risk Evaluation (SCORE) assessment tool. 453 In the UK, the QRISK s 2 online tool includes CKD as 'yes' or 'no' and therefore does not allow for level of eGFR or proteinuria. 454 The Joint British Societies Guidelines regards proteinuria as a sign of target organ damage, which conveys a risk of at least 20% in 10 years. 455 study of cardiovascular risk estimation in Chinese adults in the USA-People's Republic of China Collaborative Study of Cardiovascular and Cardiopulmonary Epidemiology (USA-PRC Study) did not include CKD as a risk factor at all. 456 It is also important to remember that in this population stroke was the predominant CVD. A review of 25 risk assessment tools identified only 2 derived from an Asian population. 457 However, links between GFR categories and CVD events are evident in the Asian population, for example in the Japanese Gonryo study. 458 A prospective study in a general Japanese population demonstrated links between lower GFR, high creatinine levels, and proteinuria with cardiovascular mortality particularly stroke. 459 In Chinese patients who were at least 50 years old and either had existing CVD or were at high risk, 34% had an eGFR o60 ml/min/1.73 m 2 and eGFR o45 ml/min/1.73 m 2 was found to be an independent predictor of all-cause and cardiovascular death. 460 In a population-based study of 2353 people aged over 40 years in Beijing, an eGFR o90 ml/min/1.73 m 2 was associated with increased CVD risk, and for each CKD category stroke was more prevalent than MI. 461 In India the increasing prevalence of type 2 diabetes is driving an increase in CKD and both are associated with increased cardiovascular risk. In CKD patients attending one clinic in North India, 28% had diabetes, 27% were overweight, and 92% had hypertension. Metabolic syndrome as defined by the International Diabetes Federation (IDF) 2007 guidelines was present in 39% and more frequent in women. 462

A full CVD risk assessment in a person with CKD should include an estimate of GFR and a quantitative assessment of albuminuria. Cystatin C may be helpful at risk stratifying those at intermediate risk.

The key aspect of these recommendations is to ensure that people with CKD are not deprived of treatment strategies known to be effective in general populations.

Many of the traditional cardiovascular risk assessment tools do not adjust for the presence of early CKD. Any tool should also adjust for level of eGFR because of increasing risk associated with lower levels of kidney function. The Framingham risk equation underestimates true events in a CKD population, but no validated different tools exist at present which better quantify cardiovascular or mortality risk in CKD populations.

Proteinuria is considered to be a sign of target organ damage and thus associated with high cardiovascular risk. However, assessment of risk should also include the presence of albuminuria. Few studies exist which demonstrate that targeting lowering of proteinuria results in reduced cardiovascular risk, though a number of studies which have targeted interruption of the RAAS (and in which lowering of urine protein has also been shown) have demonstrated a benefit.

An appropriate risk assessment tool should be available to assess risk in people with CKD. Addition of the presence of CKD to conventional risk factors in the Reykjavik population increased discrimination but did not increase risk to the same degree as smoking or diabetes. 463 In the Framingham Heart Study, GFR category 3b (GFR 30-44 ml/min/1.73 m 2 ) was associated with CVD but not equivalent to previous CVD. 464 ifestyle modification has not been studied in large trials in people with CKD but smoking cessation, achievement of optimum weight, regular exercise, and salt restriction should be seen as reasonable aims.

It is presently unclear whether children with CKD and elevated lipid levels will benefit from lipid-lowering strategies with no prospective trials ongoing in this area. It is hoped that data from both CKiD 55 and the 4C trials 78 may be able to address these shortcomings.

However, given that these children demonstrably have elevated risk of cardiovascular and atherosclerotic disease (see Recommendation 4.1.1), that there are data supporting the use of a number of statins in the pediatric population, 465 and that the adult evidence for benefit of statins in a subset of the SHARP trial 449 with a GFR o60 ml/min/1.73 m 2 exist, it would seem reasonable to consider the use of such drugs in children with CKD and elevated lipids.

Recommendations from 2006 441 for use of dietary modifications, followed by statins in children older than 8 years of age with persistent elevation in LDL-C levels, have been endorsed by the American Academy of Pediatrics. However, at the time of publication of these guidelines, the KDIGO Dyslipidemia Work Group has suggested that statin therapy may not be appropriate.

Age-and renal function-adjusted doses of such drugs should be carefully considered prior to any therapy being initiated (see Recommendation 4.4.1).

Regarding diabetes control, treatment in keeping with national and international diabetes recommendations is prudent. Note is made that there are specific caveats with respect to drugs and side effects that are important (see Recommendations 3.1. 15

-3.1.18).

There is no literature in the area of antiplatelet agents in atherosclerotic disease in the subset of children with CKD and the suggestion to offer antiplatelet agents does not apply to pediatric practice.

This statement is intended to remind clinicians that although the prevalence of fluid overload and heart failure increases with lower GFR categories, BNP becomes less reliable as a predictor of fluid overload and heart failure at lower GFRs. While it is associated with worse outcomes, cutoff values indicative of heart failure in general populations may or may not be appropriate and changes in values with treatment may or may not have the same meaning.

Natriuretic peptides belong to a family of circulatory peptide hormones from either myocardial cell origin (atrial natriuretic peptide [ANP] and BNP) or endothelial cell origin (C-type). 491, 492 They play an important role in regulating BP and body fluid volume by their natriuretic and diuretic actions, arterial dilatation, and inhibition of the RAAS. 493 atriuretic peptides for the diagnosis of CHF have been a diagnostic breakthrough in cardiology where determination of their concentration in serum can help identify patients with left ventricular systolic dysfunction. 494, 495 oncentrations of natriuretic peptides increase in people with CHF and other CVDs as a consequence of pressure and volume overload. 496, 497 Among people with progressive LVH, concentrations of NT-proBNP are typically elevated in proportion to the degree of left ventricular mass increase.

Overall, BNP levels provide a better index of left ventricular mass and load than do ANP levels and BNP has emerged as a superior biomarker to ANP for clinical applications involving CHF and left ventricular dysfunction. 491, 498 NT-proBNP may have analytical advantages over BNP because of greater stability due to a longer half-life. The cause of an elevated BNP level is multifactorial in origin and may reflect cardiac dysfunction, and/or changes in renal function. 499 Since renal dysfunction intrinsically was shown to affect BNP levels in some studies, the diagnostic value of BNP levels in the presence of CKD has been questioned. 500, 501 arlier research hypothesized that measurement of natriuretic peptides could be of use in monitoring excess fluid volume and dry weight in people requiring dialysis, 502, 503 but this remains unproven and the significance of plasma natriuretic peptides and their clinical role in dialysis remains unclear. 491 5] [506] To test this hypothesis, Tagore et al. studied BNP levels in a cohort of 143 clinically euvolemic subjects with CKD in whom absence of heart disease was clinically validated and found that plasma BNP levels were independent of GFR. 504 Suresh and Farrington 507 studied people on dialysis and concluded that BNP levels were predictive of presence of left ventricular dysfunction, cardiac events, and survival in the presence of ESRD, suggesting that BNP levels may be informative across the full range of renal function and even in its absence. As previously established by several studies, the level of NT-proBNP is a strong prognostic marker in both the general population 508 and in various disease states, e.g., acute and CHF, 509, 510 coronary heart disease, 511, 512 and hypertension. 513

The issue of how to differentially interpret BNP in the presence or absence of CHF and within the context of declining renal function has received considerable attention but remains incompletely resolved from a clinical perspective. Changes in either renal or cardiac function could potentially impact levels of natriuretic peptides and incomplete knowledge of an individual's clinical status relative to the degree of cardiac pathology or renal dysfunction could confound interpretation of BNP levels. Given the cost of biomarkers assays and the uncertainties related to interpretation of serum levels of BNP/NT-proBNP in people with CKD, competing priorities for health-care resource may dictate reliance on clinical evaluation and local practices of care in some areas of the world. Until better data are available, clinicians are asked to use this laboratory measurement with caution as a diagnostic test for heart failure in those with CKD.

Clarification of issues and key points

Natriuretic peptides may be surrogate markers for prediction of mortality in people with CKD reflecting the association of mortality with left ventricular dysfunction and LVH. Before routine measurements of these biomarkers are recommended, their utility in guiding or changing clinical practice should be assessed.

There is robust literature in both children and neonates regarding both the normative values of BNP 514 and its value in predicting outcomes of pediatric heart failure. 515 To date no studies in children specifically address the issue of reduced GFR in this population. However, application of similar principles would likely apply.

Evidence Base cTnT and cTnI are low-molecular-weight proteins that form part of the troponin complex and are integral components of the myofibrillar contractile apparatus of the heart. 527 Loss of integrity of cardiac myocyte membranes causes release of cardiac troponins into the circulation, which can be detected by highly sensitive assays developed for cTnT and cTnI to diagnose ACS. 521 A potent stimulus for the release or production of natriuretic peptides is mechanical stretching, 528 whereas plasma cTnT specifically and sensitively reflects myocardial injury and is considered to be an index of irreversible myocardial change. 521 In addition, cTnT levels can predict multi-vessel CAD in people requiring dialysis. 529 owever, the significance of screening people with CKD for CAD using these cardiac biomarkers is questionable 530 since increases in serum cardiac troponin concentration can occur in the absence of an ACS. 531 ost studies 517, [532] [533] [534] [535] [536] [537] [538] [539] [540] [541] [542] [543] [544] [545] have focused on people with ESRD where increases in serum cTnT concentrations have been observed in 20%-90% of subjects 540 but generally much lower when cTnI was measured. Information about cardiac troponins and their relationship with comorbidity is sparse in people with CKD who are not receiving dialysis treatment. 526, 527, 546, 547 Increased cardiac troponin concentrations may occur early in CKD, including GFR categories 30-59 ml/min/1.73 m 2 , and more commonly as CKD advances.

Non-invasive testing

Most studies of cardiac evaluation in people with CKD have involved candidates for kidney transplantation in order to identify existing cardiac conditions amenable to risk modification and to exclude people with short expected survival due to cardiac morbidity. Among the tests for cardiovascular assessment, coronary angiography is considered invasive, expensive, and associated with risks such as contrast-induced nephropathy and cholesterol embolism. When trying to detect CAD or predict future cardiovascular events in people with CKD, nuclear imaging modalities using thallium tracers have shown conflicting results, especially in the context of small vessel disease. Clinicians should be aware of the limitations of radionuclear testing as a screening tool for significant CAD given the limitations of the test. Exercisedependent techniques are limited by poor exercise tolerance of many subjects and people with CKD frequently have cardiac evaluation performed with pharmacological agents.

The prognostic value of myocardial perfusion studies has been shown with other perfusion tracers. For example, in a study of 126 people with ESRD who underwent technetium-99m myocardial perfusion studies as part of their pretransplant assessment, the presence of a reversible defect was associated with 3 times the risk of post-transplant cardiac events (HR 3.1; 95% CI 1.1-18.2) and nearly twice the risk of death (HR 1.92; 95% CI 1.1-4.4) compared with normal test results. 571 e Lima et al. 572 prospectively studied 126 renal transplant candidates clinically classified as moderate (age 450 years) or high (diabetes, extra cardiac vascular disease, or known CAD) coronary risk with myocardial perfusion studies, dobutamine stress echocardiography, and coronary angiography. Significant CAD, defined as greater than 70% stenosis in 1 or more major epicardial artery on angiography was found in 42% of the sample. After a median follow-up of 46 months, clinical risk stratification and coronary angiography predicted major cardiac events, but myocardial perfusion studies and dobutamine stress echocardiography did not.

Newer imaging techniques are under current evaluation but a review here is beyond the scope of this guideline; these techniques include: stress myocardial perfusion single photon emission computed tomography (SPECT); 557,573-576 18 F-BMS, a novel fluorine-based myocardial perfusion tracer; 557, 577 and gated imaging using radio-labelled ammonia ( 13 NH 3 ).

The statements presented here are intended to inform clinicians caring for those with CKD or at risk for CKD with respect to common clinical situations or exposures which may put people at risk for AKI or progression of CKD. 13 Wherever possible, people with CKD should receive the same treatment as those with normal renal function. However, the dosages may need adjustment according to GFR.

There are medicines whose toxicity is worsened in acute illness particularly in a setting of dehydration such as diarrhea and vomiting. General advice about appropriate dosing and when to restart these agents should be given to people taking these drugs during intercurrent illness, together with a recommendation for consultation with a health-care professional as soon as possible.

Use of herbal and over-the-counter medicines is very common worldwide and some (such as those containing aristolochic acid) 595, 596 are known to be nephrotoxic. There is no good quality safety or efficacy data for many of these compounds.

Table 32 details specific advice for various classes of drugs where CKD may be an issue. These include RAAS blocking agents, 262 beta-blockers, analgesics, antibiotics, lithium, 597 hypoglycemic agents, [598] [599] [600] lipid-lowering agents, 449, [601] [602] [603] [604] certain chemotherapeutic agents, and anticoagulants. 605

This guidance is based upon knowledge of pharmacology that has universal relevance. The main international implication is centered on costs of some newer therapies compared to the older ones. Somewhat paradoxically, as the weight of evidence resides mainly with agents that have been available for longer, they have the advantage of being less costly, and have the side effects that are well documented; thus many of these older agents are preferred.

No specific recommendation for or against the use of a BSA adjusted eGFR in relation to drug dosing can be made in children with CKD as the majority of drug studies have been performed in adult males and extrapolated to children without consideration for BSA and/or pediatric renal function or clearance.

The exception to this rule would be that for any drug where pediatric pharmacokinetic or pharmacodynamic studies exist, the method used in calculating the effect of renal function should be used when estimating the need for dose adjustments or modifications for the individual patient.

Numerous resources for dose adjustments for pediatric CKD and ESRD patients exist, including those found in numerous textbooks 606, 607 and online resources. 608 n additional value of dedicated pediatric renal multidisciplinary teams, in terms of caring for children with CKD and ESRD, is their ability to provide anticipatory guidance for the patients and families. All such teams should at the least provide written or online information to their patients and families directing them to seek advice in situations where they may be prescribed medications from other providers or may be seeking over-the-counter drugs or supplements. The presence of trained pediatric pharmacists as part of such teams can be invaluable in achieving such support and education for both families as well as the CKD health-care providers and community resources such as local pharmacists.

LIMITATIONS

People with CKD are often excluded or not identified from trials of medications for non-renal disease. Recommendations are partly based upon knowledge of pharmacology rather than controlled trials in carefully defined populations.

National and international research groups, and those with CKD-focus organizations (International Society of Nephrology, International Federation of Kidney Foundations, and other national bodies) should ensure adequate representation of people with CKD in clinical trials, leading to an improved understanding of pharmacodynamics of those with CKD.

Use of iodinated radiocontrast media has been associated with AKI with reported rates of 0-11% depending on the population under study, the type of agent that is used, and the definition of nephrotoxicity. 609 The following recommendations are concordant with those from the American College of Radiology (ACR), 610

These statements have been worded in order to inform safe radiological investigation of people with CKD and to avoid potential nephrotoxcity that can be associated with radiological imaging.

Radiocontrast media associated AKI is a largely preventable cause of morbidity and mortality. There is no internationally agreed definition but most studies use an increase in SCr of 40.5 mg/dl (44 mmol/l) and/or a 25% increase from baseline SCr within 3 days of the procedure. Numerous studies of preventative strategies have been performed with the following conclusions: a) High osmolar agents pose a greater risk of AKI in people with CKD. 609 b) Iso-osmolar agents compared to low-osmolar agents are associated with lower rates of AKI in some but not all studies. Wherever possible iso-osmolar agents should be used in people with CKD at high risk for AKI (although these tend to be more expensive). 612 Although risk for AKI increases with GFR o60 ml/min/ 1.73 m 2 , the rates are particularly high (7.8% in one study) when GFR is o30 ml/min/1.73 m 2 . Implementing preventative strategies for all with a GFR o60 ml/min/ 1.73 m 2 may not be practical but a graded risk assessment taking into account all factors may be more realistic. Some guidelines such as American College Radiology 610 and ESUR 611 provide a checklist as a means of identifying patients at risk of AKI before investigation. d) Extracellular volume expansion is widely recommended although there are few good quality trials on which to base an ideal protocol. 609 0.9% saline given by continuous infusion appears superior to 0.45% saline or bolus injection and there is no demonstration of consistent superiority of sodium bicarbonate over saline. Current guidance suggests either infusion of 1 ml/kg body weight/ hour for 3-12 hours before and after the procedure or 100 ml/hr, beginning 6 to 12 hours before and continuing 4 to 12 hours after intravascular iodinated contrast medium administration. 609 ,610 e) Use of N-acetylcysteine or ascorbic acid as preventative measures has not been shown to be a consistent benefit.

This guidance has universal relevance although there are cost implications as the iso-osmolar contrast media are more expensive.

Some of the guidance is based upon limited evidence and there is a need for more research into simple preventative measure such as pre-investigation rehydration (see below). There has not previously been a universal definition for AKI following administration of contrast media. However, recommendations from the KDIGO AKI Guideline suggest that the same general AKI definition and staging be used for changes in kidney function, irrespective of etiology.

Prospective studies using direct measures of GFR before and after administration of radiological contrast media are required to help define the incidence of AKI. Such studies would also be able to validate creatinine or other estimates of GFR in people undergoing radiological investigation. Prospective controlled trials of rehydration using different fluids (saline, bicarbonate, Hartmann's) and validated estimates of GFR are urgently required.

Definitive studies of N-acetylcysteine and other antioxidants would help determine their usefulness or otherwise.

Gadolinium-containing contrast media

Gadolinium is a rare earth element that is naturally highly toxic. When bound to proprietary chelating agents, it is essentially biologically inert in people with normal renal function and provides excellent contrast during MRI. These chelates are excreted unchanged by the kidneys by glomerular filtration and have much lower direct nephrotoxicity than conventional radioiodine contrast media. 613 However over 200 cases of a scleroderma-like condition now termed nephrogenic systemic fibrosis (NSF) following gadolinium use in patients with CKD have been reported. 613, 614 .3: We recommend not using gadolinium-containing contrast media in people with GFR o15 ml/min/ 1.73 m 2 (GFR category G5) unless there is no alternative appropriate test. (1B) 4.5.4: We suggest that people with a GFR o30 ml/min/ 1.73 m 2 (GFR categories G4-G5) who require gadolinium-containing contrast media are preferentially offered a macrocyclic chelate preparation. (2B)

These statements have been worded in order to enable safe administration of gadolinium to people with CKD. As with all tests requested in the CKD population, clinicians should be aware of the risk-benefit ratio of the use of gadolinium in people with GFR 15-29 ml/min/1.73 m 2 .

NSF is an untreatable and sometimes fatal condition that complicates the use of gadolinium-containing contrast media in people with CKD. Prevention is therefore the best approach with avoidance of gadolinium exposure unless clinically indicated and to use the lowest risk agent at the lowest dose. 613, 615 lthough the risk of AKI with iodinated contrast media is much greater than that for NSF with gadolinium, the former is treatable with dialysis whereas the latter is not. ] [615] A recent meta-analysis and review have highlighted those patients most at risk and quantified an OR for NSF of between 20-50 for those with a GFR o15 ml/min/1.73 m 2 . 614 hile there is general agreement that patients with a GFR 415 ml/min/1.73 m 2 are at increased risk, it is not possible to derive a precise estimate. No patients with a GFR 430 ml/ min/1.73 m 2 have developed NSF without concomitant liver failure. 614 here is some suggestion that the type of gadolinium preparation plays a role: 614, 615 Linear chelated preparations such as gadodiamide may be more likely to cause NSF and should be avoided when GFR is o30 ml/min/1.73 m 2 . Gadoteridol, gadobutrol, or gadoterate should be considered if MRI with contrast is clinically essential. 610, 613, 615 Moreover, as gadolinium is freely dialysed, 616 most guidelines recommend dialysis in patients with a GFR o15 ml/min/1.73 m 2 or for those already on dialysis immediately after (and perhaps repeated 24 hours later) completion of the procedure. 610, 615 The role of dialysis in people with GFR above 15 ml/min/1.73 m 2 is uncertain.

This guidance has universal relevance although there are cost implications as the non-linear chelated preparations are more expensive.

Regarding both Recommendations 4.5.3 and 4.5.4, a number of considerations specific to the use of gadolinium preparations in young children and neonates must also be considered in addition to the general admonishments against their use in situations of GFR o30 ml/min/1.73 m 2 . In particular, the FDA currently does not license any gadolinium-based contrast agent (GBCA) product for use in children less than 2 years of age; and likewise the European Medicines Agency cautions against the use of any GBCA in a child less than 1 year of age.

In addition, the ability to accurately estimate the relative value of a neonate or young infant's GFR leads to great difficulty in terms of assigning risk of GBCA exposure if one bases this on renal clearance. In a recent paper by Meng and colleagues, 617 they surveyed a worldwide group of both cardiologists and radiologists with respect to their use of gadolinium in their pediatric MRI practice. While 93% of the respondents did evaluate renal function in some or all of their patients, only a slight majority (54%) used an estimating formula, most often the Schwartz equation, with the remainder relying on SCr alone (31%) or urine output (6%). Perhaps of most concern was that renal function was assessed in only 33% and 31%, respectively, of patients classified as 'all neonates' or 'all patients o1 week of age.' Equally concerning was the fact that 13% of the respondents would give gadolinium to some of these children in the face of a GFR o30 ml/min/1.73 m 2 .

In recognition of our inability to accurately measure GFR in the neonate and, by extension, the clearance of compounds such as gadolinium, all nephrologists and radiologists must exercise caution in terms of use of GBCA in this potentially high-risk population, and all other imaging modalities should be considered prior to choosing one requiring gadolinium exposure.

The evidence is largely based upon case series rather than prospective studies or RCTs.

As for iodinated contrast media, a prospective study of people with CKD undergoing nuclear MRI with gadolinium contrast would help define change in GFR and validate estimators. Because NSF is such a serious condition, an RCT of dialysis in people with GFR o30 ml/min/1.73 m 2 would help to determine risk-benefit in these patients, though recruitment may be difficult due to potential ethical concerns.

Bowel preparation

The increasing use of colonoscopy as a screening tool for bowel cancer has resulted in many people undergoing bowel Kidney International Supplements (2013) 3, 91-111 105 c h a p t e r 4 preparation with oral sodium phosphate-containing preparations. Case reports of acute and late irreversible renal failure with biopsy-proven phosphate deposition have led to a new disease entity termed acute phosphate nephropathy. 618, 619 ess than 40 definite cases have been reported and these have been extensively reviewed. 4.5.5: We recommend not to use oral phosphate-containing bowel preparations in people with a GFR o60 ml/min/1.73 m 2 (GFR categories G3a-G5) or in those known to be at risk of phosphate nephropathy. (1A)

This statement has been worded in order to enable safe bowel preparation in people with CKD who need to undergo investigation of bowel disease.

Electrolyte disturbances that are sometimes severe and include hyperphosphatemia, hypocalcemia, hypo-and hypernatremia, and hypokalemia have been reported in normal volunteers undergoing oral phosphate bowel preparation. 620 Renal injury has been reported in a small number of people although the condition is likely to be underrecorded. A recent study from Iceland estimated the incidence to be around 1 per thousand doses 621 but others would suggest incidence rates of between 1% and 4%. 618, 619 wo broad patterns of renal injury have been described. An early symptomatic response associated with severe hyperphosphatemia and hypocalcemia and a later (days to months) irreversible kidney injury associated with a specific tubulointerstitial calcium phosphate deposition. 618, 619 he following people are said to be at particular risk although the link to kidney injury is associative in many cases and firm evidence is lacking: Although the FDA has banned oral phosphate solutions, there is no qualitative difference with tablet preparations. Both should be avoided in people at risk and this is the current recommendation of the American Society for Gastrointestinal Endoscopy. 622 ere is some debate as to whether the cause of the kidney injury is entirely due to dehydration rather than phosphate use per se. 623 However, it is hard to understand why calcium phosphate deposits occur and cause late renal impairment if dehydration was the only factor.

There is a single RCT of phosphate versus non-phosphate preparations but assessment of renal function was limited to change in SCr and GFR at baseline is not reported. 624 otwithstanding these limitations, there were greater changes in serum potassium, calcium, and phosphate in those given sodium phosphate-containing preparations.

As there are non-phosphate-containing bowel preparations available, these should be used in all the above groups (and arguably in all people given the biochemical abnormalities observed in normal volunteers). As for radiocontrast media, rehydration with saline may be required in the frail and ill irrespective of the bowel preparation that is used.

This guidance has universal relevance but non-phosphatecontaining bowel preparations are more expensive, so the use of these agents may differ around the world.

The data are based upon case series with a limited number of affected individuals and retrospective population studies.

Prospective study in people with normal renal function and those with different severities of CKD are urgently required in order to define the acute biochemical and metabolic effects of phosphate-containing bowel preparations. There is also a need for a study of all people undergoing bowel preparation with whatever preparation in order to explore the effects on GFR on the incidence of this complication. More definitive exploration of rehydration therapy (type and volume) in people with CKD undergoing bowel preparation is urgently needed.

4.6 CKD AND RISKS FOR INFECTIONS, AKI, HOSPITALIZATIONS, AND MORTALITY

The following section gives guidance for the care of people with CKD given that they are at increased risk for a number of events such as infections, AKI, CVD, hospitalizations, and mortality. Appreciating that increased risk and implementing some of the recommendations below may result in improved outcomes for people. It will be important to develop policies and robust research agendas to address areas which do not have a substantial evidentiary base.

CKD and risk of infections

CKD is associated with significant major infectious complications, which occur at rates 3 to 4 times the general population. Infection is an important cause of morbidity and mortality among patients with kidney failure and is the 106 Kidney International Supplements (2013) 3, 91-111 c h a p t e r 4 second leading cause of death following CVD. CKD may be a risk-multiplier for acute infectious disease-associated mortality, as it is for CVD. Despite a less effective response to vaccination, there are data suggesting benefit from immunization among people with CKD as in the general population. 4.6.1: We recommend that all adults with CKD are offered annual vaccination with influenza vaccine, unless contraindicated. (1B) 4.6.2: We recommend that all adults with eGFR o30 ml/ min/1.73 m 2 (GFR categories G4-G5) and those at high risk of pneumococcal infection (e.g., nephrotic syndrome, diabetes, or those receiving immunosuppression) receive vaccination with polyvalent pneumococcal vaccine unless contraindicated. (1B) 4.6.3: We recommend that all adults with CKD who have received pneumococcal vaccination are offered revaccination within 5 years. (1B) 4.6.4: We recommend that all adults who are at high risk of progression of CKD and have GFR o30 ml/min/ 1.73 m 2 (GFR categories G4-G5) be immunized against hepatitis B and the response confirmed by appropriate serological testing. (1B) 4.6.5: Consideration of live vaccine should include an appreciation of the patient's immune status and should be in line with recommendations from official or governmental bodies. (Not Graded) 4.6.6: Pediatric immunization schedules should be followed according to official international and regional recommedations for children with CKD. (Not Graded)

CKD is associated with alterations in primary host defense mechanisms and increases the risk of bacterial infections (Table 33 ). Epidemiological study suggests that the 3 most commonly seen infectious complications in the CKD population are: urinary tract infection, pneumonia, and sepsis. In the general population, there is strong evidence that preventive measures are effective in adults and there are data suggesting benefit from immunization in people with CKD.

6] [627] [628] However, few epidemiologic reports have addressed the risk of infections in people with CKD not treated with dialysis. 629, 630 ata from the US Renal Data System (USRDS) suggest that higher rates of hospital admission because of septicemia are noted in people with CKD compared with those without CKD. 631 Comprehensive studies of the absolute rates, risk factors, clinical course, and outcomes of different types of clinically relevant infections across the spectrum of CKD are not available. Among people with CKD, very few studies have examined the incidence or prevalence of infections and no published data describe GFR category-specific infection rates. Among Medicare beneficiaries aged more than 66 yr, people with diagnosed CKD seem to have substantially higher rates of hospitalization for diagnoses of pneumonia and sepsis compared with people without diagnosed CKD. 628 In addition to an increased incidence of being hospitalized with infections, people with CKD have longer lengths of hospital stay during infection-related admissions compared with people without CKD. 632 Among USRDS data admission rates for all causes, CVD and infection, are 38-46% higher for those with CKD than for those without. 633 Rates for pneumonia in CKD were nearly three times higher than those for non-CKD. Hospitalizations for bacteremia/septicemia, were nearly four times higher for people with CKD compared to those without. Hospitalization rates for urinary tract infections were three-fold higher for people with CKD.

] [638] However, these issues have not been adequately investigated in people with CKD.

There is a growing body of evidence in the general population for reduction in infections, hospitalizations, and mortality as a result of immunizations. Current data suggest that vaccination is an underused prevention strategy in the CKD and ESRD populations. 639 Potential barriers to immunization that are specific to the CKD populations have not been systematically examined. ] [642] Studies that have examined vaccination in the setting of CKD or ESRD have been limited by small study size, variable follow-up, and ascertainment of surrogates for vaccine effectiveness such as antibody response and rate of antibody decline after vaccination as opposed to vaccine efficacy for preventing infection. 643 nfluenza A and B vaccine. Despite potentially impaired antibody responses, a 2-year analysis of US Medicare claims data found that people vaccinated against influenza A and B on dialysis had a substantially lower chance of any-cause hospital admission and any-cause death than those patients not vaccinated on dialysis. 644 This finding might indicate clinical effectiveness of vaccinating this population but its observational design might also reflect differences in the underlying clinical status among people vaccinated and not 625 Immunosuppressive therapy 628 Nephrotic syndrome 634 Uremia Anemia and malnutrition 635 High prevalence of functional disabilities Abbreviation: CKD, chronic kidney disese Kidney International Supplements (2013) 3, 91-111 107 c h a p t e r 4 vaccinated. No unique adverse events related to influenza vaccine have been identified in people on dialysis.

Pneumococcal vaccine. People with kidney disease vaccinated with the pneumococcal vaccine seem to develop different serotype-specific titers, develop lower levels of antibody titers, and have a more rapid loss of antibody titers as compared with healthy control subjects. 639, 645, 646 ractitioners should be aware of the impact of specific vaccines on responsiveness and duration of responsiveness. Revaccination practices will be dictated by that knowledge.

Hepatitis B vaccine. Widespread hepatitis B virus (HBV) vaccination at the onset of dialysis has led to a marked reduction of HBV infections in people with ESRD, although improved screening of blood products and dissemination of recommendations for reducing the spread of HBV infections in dialysis units have also likely contributed. 647 Among people with moderate to advanced CKD, hepatitis B vaccination responsiveness has been shown to range from approximately 60 to 80% depending on the dosage, number of administered vaccines, and study population. Although findings have been inconsistent as to whether the level of GFR affects vaccine responsiveness in people with CKD 640, 642 those with higher GFR are more likely to respond with seroconversion, independent of other factors. 640 . aureus vaccine. StaphVAX has not been shown to be efficacious in reducing the risk for Staphylococcus aureus bacteremia in people on hemodialysis. 648, 649 No data are published in people with CKD.

Live vaccines. Due to the fact that people with CKD are often immunocompromised, live vaccines should only be used with caution on an individual basis.

In summary, although some vaccines (like influenza) in usual doses provide protection, other vaccines (HBV and pneumococcal) require more frequent dosing or larger doses to achieve and maintain protective antibody titers. Frequency and type of vaccination will vary according to local circumstances and prevalence of disease.

The availability of different vaccinations may vary worldwide, as does the prevalence of specific bacterial, viral, and other infections. It is reasonable to offer individuals appropriate immunization according to local practices.

Vaccines for influenza, hepatitis B, and pneumococcus are currently recommended for people with CKD by the local, regional, or national advisory committees on immunization practices from most countries.

Current recommendations are to:

K Provide influenza vaccination annually to people with CKD.

K Provide pneumococcal vaccine with a single booster dose 5 years after the initial dose.

K Provide HBV vaccine to people with CKD who are likely to require RRT. Although the recommendation is to give the HBV vaccine during more severe CKD (GFR o15 ml/ min/1.73 m 2 ), it may be preferable to give this earlier to maximize the chances of achieving immunity; there are data to support this practice. 640 This would also ensure that all patients are immunized against HBV before receiving a transplant. As protective antibody levels may fall, this should be checked (possibly annually) with booster doses given if appropriate.

Much remains to be understood concerning impaired host response to infection in patients with CKD.

K Studies should be undertaken to determine the absolute rates, risk factors, and clinical course of different types of clinically relevant infections across the spectrum of CKD, by GFR and albuminuria category, and by cause.

K The outcomes across the range of acute infections in CKD population need to be ascertained.

K Studies should be undertaken to assess the rate of decline of antibody titers post-vaccination and the efficacy of immunization in people with CKD.

Current immunization schedules for children are regularly updated by both the US Centers for Disease Control and Prevention 650 and American Academy of Pediatrics. 651 urrent and comprehensive immunization recommendations for children with CKD have been published by Neu in 2012. 652 he paper addresses key issues regarding the use of vaccines in CKD pediatric populations who are receiving concomitant immunosuppression and in those awaiting transplantation. The need for, and interpretation of, protective antibody levels for those vaccines where this is indicated is described.

An oversimplified summary of the recommendations would be to provide all recommended childhood vaccines to every child with CKD with the exception of any live viral vaccine in a child receiving immunosuppressive medications. Likewise children on dialysis should not receive the live attenuated influenza vaccine although the inactivated version can and should be given to all children with CKD on an annual basis otherwise. Pneumococcal vaccination is particularly important in children with nephrotic syndrome and those with CKD, and current vaccination schedules and products should be carefully reviewed to ensure proper serotype coverage is being provided. Hepatitis B status and vaccination are of extreme importance in all children who may go onto dialysis -and specific recommendations for ongoing monitoring and interpretation of antibody levels should be carefully reviewed.

CKD and risk of AKI

Due to the epidemiological association between CKD and AKI and the number of observational studies reporting an association between pre-existing CKD and AKI, CKD is considered the most consistent pre-existing condition associated with a high risk of AKI. However the potential linkage between patients with AKI, CKD, and ESRD has been inadequately studied to date and remains ill defined. This section describes AKI as a complication which needs to be managed in those with CKD. Given its association with progression, it is also described in that section. 4.6.7: We recommend that all people with CKD are considered to be at increased risk of AKI. (1A) 4.6.7.1: In people with CKD, the recommendations detailed in the KDIGO AKI Guideline should be followed for management of those at risk of AKI during intercurrent illness, or when undergoing investigation and procedures that are likely to increase the risk of AKI. (Not Graded)

CKD is designated as a risk factor for AKI because of the epidemiological association between the two. 263, 264 6] [267] [268] [269] [270] [271] CKD is a potent predictor of acute decline in kidney function following exposure to radiocontrast, 272 major surgery, 273 and other medical conditions. 274 su et al. 14 compared the pre-hospitalization MDRD GFR of 1764 adult members of the Kaiser Permanente Northern California health-care system who developed dialysis-requiring AKI during hospitalization with 600,820 individuals who did not. Compared with a reference baseline GFR of Z60 ml/ min/1.73 m 2 , a baseline GFR of 45-59 ml/min/1.73 m 2 was associated with an adjusted OR of in-hospital AKI of 1.66 (95% CI 1.40-1.97). For GFR values of 15-29 ml/min/1.73 m 2 , the adjusted OR for in-hospital AKI was 20.42 (95% CI 17. 40-23.96). The presence of diabetes, hypertension, and proteinuria increased the likelihood of developing in-hospital AKI, with adjusted ORs of 1.99 (95% CI 1.78-2.23), 1.55 (95% CI 1.37-1.76) and 2.84 (95% CI 2.52-3.19), respectively. The authors concluded that CKD is the main risk factor for AKI during hospitalization. A contrasting approach by Singh et al. defined AKI as dialysis-requiring acute renal failure. 275 ecause the clinical decision to dialyze a patient is frequently influenced by a higher overall SCr, presence of hemodialysis access, or consideration of inevitable progression to ESRD, this definition of AKI could bias toward capturing more AKI cases in CKD patients. Moreover, in patients with advanced CKD, the progression of CKD to ESRD may sometimes be difficult to separate from acute-on-chronic renal failure. A cohort study by Lafrance et al. This statement is worded this way to make clinicians aware that people with CKD and heart failure should receive at least equal benefit from heart failure therapy as those without CKD, but that heart failure therapies (in particular increase of RAAS blockade and diuretic therapy) may lead to significant changes in GFR and serum potassium concentrations. This does not imply that such therapy should be avoided but only that clinicians are cognizant of this possibility, monitor it, and understand it in the context of individual risks and benefits. Heart failure is a complex clinical syndrome which can be caused by any structural or functional cardiac disorder that impairs the pump function of the heart and has a high mortality. Within the general population, the commonest causes of heart failure are ischemic heart disease causing left ventricular systolic dysfunction, and hypertensive heart disease with left ventricular hypertrophy and diastolic dysfunction. Thus people with CKD are at increased risk of both. Evidence-based medication for heart failure impacts on GFR and prescribers need to be alert to this. Changes in GFR are often transient and the downward trajectory GFR is not sustained if all other aspects of care and clinical status are stable. Monitoring and close follow-up are required.

In an outpatient setting, normal GFR is unusual in heart failure. A study from the Alberta Heart Function Clinic found that in people with an ejection fraction of r35%, GFR categories G3a and G3b (GFR 30-59 ml/min/1.73 m 2 ) were present in 40% and 16% of people were GFR categories G4 or G5 (GFRo30 ml/min/1.73 m 2 ). 466 This study demonstrated a 1% increase in mortality associated with each 1 ml/min fall in CrCl demonstrating the clear link between kidney function and outcome for people with CKD and heart failure. Metaanalysis of 16 studies and over 80,000 people with heart failure by Smith et al. showed that renal impairment was present in 63% and was associated with increased mortality across the range of kidney function, with an adjusted HR of 1.56 (95% CI 1.53-1.60). 467 In the Candesartan in Heart Failure-Assessment of Reduction in Mortality and Morbidity (CHARM) Program with candesartan in heart failure, 36% of subjects had eGFR o60 ml/min/1.73 m 2 which was associated with increased mortality and hospital admission regardless of ejection fraction. 468 The Digitalis Intervention Group (DIG) identified a GFR of 50 ml/min as a risk threshold for increased mortality risk in heart failure. 469 Smith et al. demonstrated that 1-year mortality after admission for heart failure was 29% in people with normal kidney function but 52% in those with moderate to severe renal impairment. 470 Anand et al. also demonstrated an independent association between the presence of positive reagent strip proteinuria present in 8% of subjects and increased mortality in heart failure. 471 n the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) study of people with heart failure related to coronary artery disease (CAD), 39% had CrCl o60 ml/min (o1 ml/s). This study also demonstrated that the level of kidney function was a better indicator of poor outcome than cardiac anatomy. 472 In people admitted to hospital with heart failure, increasing SCr concentration is associated with a longer hospital stay and worse outcome. 473 VH is present in 40% of people with CKD, 474 progressively increasing as kidney function declines. 475 a et al. demonstrated LVH in 87% of people with predialysis CKD. 476 Parfrey et al. in a study of 432 people who were predialysis, found that only 16% had a normal echocardiogram while 41% had concentric LVH, 16% systolic dysfunction, and 28% left ventricular dilatation. 477 LVH is related to increased work load caused by arterial stiffness and hypertension, and at lower levels of GFR, volume overload. Alterations in electrolyte balance, anemia, bone metabolism, uremia, oxidative stress, inflammation, and other inflammatory mechanisms all play a role. 478 n the majority of people with CKD, the myocardium develops concentric hypertrophy 476 with interstitial fibrosis and CKD-associated cardiomyopathy, leading to left ventricular stiffness. 474 This results in diastolic heart failure; people with CKD have higher mortality from diastolic heart failure than systolic heart failure. 479 Diastolic heart failure is more common in people with CKD who are older females with hypertension and/or diabetes. 480 eft ventricular hypertrophy is particularly associated with anemia and a fall in Hb to less than 12.8 g/dl (128 g/l) is associated with left ventricular growth in people with early CKD. 481 Lower Hb levels are associated with increased risk of death and hospitalization in heart failure. 482 Other cardiovascular conditions, for example MI and atrial fibrillation, are more common in CKD and may exacerbate heart failure.

It is important to note that in a study of an older population (age 464 years), heart failure was an independent predictor of rapid kidney function decline. 483 tandard therapy for the management of systolic heart failure includes an ACE-I or ARB and a beta-blocker licensed for heart failure such as bisoprolol or carvedilol. Metaanalysis of 25 trials of RAAS blockade (ACE-I or ARB) in people with CKD or proteinuria, demonstrated a reduction in the risk for heart failure and reduction in cardiovascular outcomes. 484 Subgroup analysis from the Valsartan Heart Failure Trial (Val-HeFT) demonstrated the beneficial effect of valsartan in people with CKD and that valsartan reduced the eGFR by the same amount in people with and without CKD. 471 Candesartan was also clinically effective in the CHARM study regardless of underlying kidney function 468 while irbesartan was associated with a 23% reduction in hospital admissions related to heart failure in people with nephropathy due to type 2 diabetes. 485 Analysis of data on bisoprolol from the Cardiac Insufficiency Bisoprolol Study II (CIBIS II) 486 identified 32% of subjects with eGFR o60 ml/ min/1.73 m 2 . These subjects were more likely to die or be admitted to hospital than those with eGFRZ60 ml/min/1.73 m 2 . However, they showed a similar benefit from bisoprolol treatment. A post hoc analysis of data on carvedilol from the Carvedilol Post-Infarct Survival Control in Left Ventricular Dysfunction (CAPRICORN) and Carvedilol Prospective Randomized Cumulative Survival (COPERNICUS) trials identified 60.8% of participants with eGFR o60 ml/min/ 1.73 m 2 . 487 Carvedilol was well tolerated by subjects with CKD, and decreased all-cause, cardiovascular, and heart failure mortality. However, doubts were raised over the benefits when eGFR o45 ml/min/1.73 m 2 .

Aldosterone antagonists are included in standard heart failure management, usually in addition to an ACE-I or ARB, leading to concerns relating to risk of hyperkalemia, particularly in people with lower GFRs. In a study of spironolactone therapy in severe heart failure, Pitt et al. 488 included subjects with SCr concentrations up to 2.5 mg/dl (221 mmol/l). There was a 30% reduction in mortality with spironolactone and the incidence of hyperkalemia was low. However, a review of real-world practice demonstrated a significant increase in hyperkalemia with the combination of RAAS blockade and an aldosterone antagonist, highlighting the need for close monitoring with the introduction of combination therapy. 489 n the APPROACH study on the specialist management of heart failure, subjects with CAD and CKD, despite being at high risk, were less likely to be taking ACE-Is, beta-blockers, statin, and aspirin. This study demonstrated that those subjects taking beta blockers had lower mortality, however ACE-Is were only of benefit when eGFR was 460 ml/min/1.73 m 2 . 472

The treatment of heart failure is similar around the globe. The ability to closely monitor kidney function or to offer conventional therapies may differ, however. Irrespective, this statement should hold true internationally. The National Heart Care Project of community subjects admitted to hospital with heart failure studied the differences between people of black and white ethnic groups. People with worse renal function were more likely to be black, older and female, and black people had a greater prevalence of hypertension and diabetes but less ischemic heart disease. Black people had a lower risk of mortality at every level of creatinine, for every 0.5 mg/dl (44.2 mmol/l) increase in creatinine, 1-year death risk increased 10% in black people and 15% in white people. 470

Cardiorenal syndrome, an impairment of kidney function in the presence of heart disease, is a marker of worse prognosis. In addition to GFR, the presence and severity of albuminuria and anemia aid in prognostication and management. 490 here the link between LVH and heart failure in CKD is so strong and the outcome poor for people with LVH, efforts should be made to optimize care particularly BP. There is a lack of robust evidence for the optimal medical management of heart failure specifically in people with CKD; however, the prevalence of people with early CKD is so high in heart failure trials that we can apply standard treatment to these people. For those people with eGFR o45 ml/min/1.73 m 2 , the situation is less clear. 487

There are difficulties in making the diagnosis of heart failure in people with CKD, especially diastolic heart failure. Biomarkers such as B-type natriuretic peptide (BNP) may be abnormally elevated in CKD, but may or may not be as responsive to treatment or diagnostically accurate in people with CKD (see Chapter 4.2). There is little evidence to guide the management of left ventricular systolic dysfunction in people with CKD and evidence for the management of diastolic heart failure is generally lacking. However, there is evidence that medications to improve the outcome of people with heart failure are underused in people with CKD.

Appropriate management of the metabolic complications of kidney disease which can exacerbate heart failure needs to be clarified. Clinical studies are required on the role of device therapy in people with CKD (e.g., pacemakers, defibrillators, etc.).

4.2 CAVEATS WHEN INTERPRETING TESTS FOR CVD IN PEOPLE WITH CKD

BNP/N-terminal-proBNP (NT-proBNP)

As GFR diminishes, the prevalence and severity of cardiovascular abnormalities increase and are accepted as major causes of morbidity and mortality in people with CKD. The presence of congestive heart failure (CHF) in people with CKD conveys a worse prognosis than either condition alone. Therefore, early diagnosis and aggressive management of CHF are both highly desirable. A number of cardiac biomarkers (i.e., BNPs and cardiac troponins) appear to have both increasing clinical importance and increasing facility for detection and stratification of CHF. The stimulus for secretion of these biomarkers is the hemodynamic load (i.e., myocardial stretch) and their secretion is associated with the severity of CHF and the degree of left ventricular dysfunction. They are thus useful markers for diagnosis, management, and prognosis in people with normal renal function. However, when the eGFR is less than 60 ml/min/ 1.73 m 2 , the accuracy of plasma BNP and NT-proBNP levels for detection and stratification of CHF becomes unreliable and the degree of responsiveness to treatment is not known.

4.2.1:

In people with GFR o60 ml/min/1.73 m 2 (GFR categories G3a-G5), we recommend that serum concentrations of BNP/NT-proBNP be interpreted with caution and in relation to GFR with respect to diagnosis of heart failure and assessment of volume status. (1B)

Since people with ESRD with elevated levels of BNP have a higher RR of death, this biomarker could be used as an individual risk marker with the aim of identifying those at high risk. Clinical correlation is of utmost importance to ensure accurate diagnosis and appropriate therapy.

Studies to understand the variability of BNP by categories of eGFR and urine ACR, within and between individuals over time, and the response to therapy should be undertaken so as to better inform clinicians.

The relationship between renal function and BNP, the role of natriuretic peptides as markers of fluid overload and as predictors of mortality, and the utility of serial monitoring of BNP/NT-proBNP levels in people with CKD, and responsiveness to therapy remains unknown.

Troponins

In recent years newer markers of myocardial injury have been introduced into clinical practice. 516, 517 Among these, cardiac troponins have proven to be specific markers of myocardial damage. 518, 519 Cardiac troponins have been considered the gold standard biochemical test for diagnosis of myocardial damage because they have nearly absolute myocardial tissue specificity, as well as high sensitivity, thereby reflecting even microscopic zones of myocardial necrosis. 517, 520 Furthermore, increasing evidence indicates that abnormal troponin measurements identify a subgroup of patients who have an increased risk of major cardiac events 519, [521] [522] [523] [524] [525] and that measurement of cardiac troponin T (cTnT) prior to commencing renal replacement is a significant independent predictor of survival. 526 However, these markers are renally excreted and are often found to be elevated in people with CKD irrespective of specific symptomatology. Thus, there is uncertainty as to the clinical importance of their different magnitudes of elevation in CKD. There are no data on 'expected' values of these markers in the context of CKD, or at different categories of GFR and albuminuria.

4.2.2:

In people with GFR o60 ml/min/1.73 m 2 (GFR categories G3a-G5), we recommend that serum concentrations of troponin be interpreted with caution with respect to diagnosis of acute coronary syndrome. (1B)

This statement is intended to remind clinicians that isolated elevated serum concentrations of troponin (in the absence of symptoms or electrocardiographic changes) may not necessarily portend a diagnosis of ACS at lower GFR categories. While there are data linking troponin elevations with poor outcomes, the specific implications for an individual in clinical practice are not clear. Hence, this statement simply cautions the clinician with respect to interpretation but does not suggest that the laboratory values are not of significance. In a patient with clinical symptoms suggestive for ischemic heart disease, an elevated cardiac troponin I (cTnI) is suggestive for ACS.

Powerful prognostic data emerging from the dialysis population demonstrate that increased concentrations of cardiac troponins reflect either subclinical myocardial damage caused by silent ischemia or myocardial remodeling in the development of LVH. 539, 542 ncreased levels of cTnT measured with the highly sensitive assay, well below the detection range of standard assays, have been shown to be associated with cardiac structural abnormalities including LVH (both left ventricular wall thickening and dilation) and left ventricular systolic dysfunction, 548 and to have a graded association with allcause and CVD mortality independent of traditional risk factors, renal function, and levels of other biomarkers such as high sensitivity CRP and NT-proBNP.

These findings suggest that chronic elevation of troponin levels may be mediated to a greater extent by indices of heart failure (such as higher left ventricular mass, left ventricular dysfunction, or increased NT-proBNP levels) than indices of atherosclerosis or ischemia. 548

The costs of these tests, the differing sensitivity of the assays available, the paucity of data in people with CKD, and the poor correlation of serum troponin levels with ACS in people with CKD should be weighed against competing local healthcare priorities and resource before their introduction into routine clinical practice. Emphasis should be placed on the clinical context and local standard practices of care.

Troponin elevation may result from repeated episodes of clinically silent MI, 522, 549 although CAD frequently underlies troponin elevation and increased cTnT is also frequently encountered in patients at low risk for CAD. Troponin elevations are as frequent in subjects without CAD as in those with known CAD 517, [550] [551] [552] and in people with CKD, serial increasing cTn levels may be of greater utility for diagnosis of ACS. In the context of symptoms and signs of ACS, elevations of troponins should not be ignored nor incorrectly attributed to simply 'CKD.' Thus the importance of ordering the test for specific indications for those with CKD should be emphasized.

Information about cardiac troponins and their relationship with comorbidity is sparse in people with CKD who are not receiving dialysis treatment. Although elevated values for TnT are common in people with low GFR in the absence of ACS or CHF, the prevelance of elevated TnI in the absence of ACS or CHF in people with low GFR may be only 0.4-6% depending on the cutoff value chosen. 532

As pointed out by Roberts et al., 553 although management strategies in people without CKD based on these biomarkers are quite clear, in people with CKD it is not the case despite the strong data on the prognostic implications. These biochemical markers can only be useful if they are interpreted in the context of the clinical history and examination with consideration given as to what management is appropriate for each individual, and if a cardiovascular therapy that is effective in this population is identified or developed. 553 The importance of understanding and contextualizing elevations in troponin values in CKD populations cannot be overstated: under-treatment in symptomatic individuals should be avoided, and better understanding of treatment strategies in those asymptomatic individuals is the focus of ongoing study.

While normative values exist for troponin in children, 554 its utility as a general screening marker for myocardial ischemia in pediatrics has recently been called into question, 555 and no data exist relating reduced renal function and troponin levels in children.

These statements are worded in this way firstly because although people with CKD are at increased risk from cardiovascular events, observational study has shown that they are frequently discriminated against in terms of investigation and management of such events. Secondly, non-invasive cardiac tests have known additional limitations in people with CKD and such limitations and their consequences need to be clearly understood by health professionals caring for people with CKD.

Noninvasive stress testing appears to be the most common first approach to cardiac evaluation of asymptomatic patients, prompted by diabetes, age and risk-factor burden. These tests include myocardial perfusion studies, stress echocardiography, and most recently, cardiac computed tomographic angiography. However, people with CKD are underrepresented in studies evaluating the diagnostic sensitivities and specificities of noninvasive tests. Exercise ECG is limited by lack of specificity of the ST-segment response and by inability of many people with CKD to exercise to a diagnostic workload. These tests have imperfect sensitivity and specificity in people with CKD or, in the case of tomographic angiography, evaluation in this population is as yet unpublished. 556 CAD has been detected in a high proportion of people on long-term dialysis therapy. ] [560] [561] [562] Abnormalities on myocardial perfusion studies correlate well with the presence of CAD in the general population, with mean weighted sensitivity of 88% and mean weighted specificity of 74%. 563 5] [566] [567] Nonetheless, results from myocardial perfusion studies have prognostic value for cardiac events and mortality. 568, 569 In a meta-analysis of 12 studies involving thallium-201 scintigraphy and dobutamine stress echocardiography, people with ESRD with inducible ischemia had approximately 6 times the risk of MI and 4 times the risk of cardiac death as those without inducible defects. 570 oreover, subjects with fixed defects also had nearly 5 times the risk of cardiac death.

People with CKD who are being investigated prior to transplantation should be assessed according to the national and international cardiology guidelines and taking into account local practice and availability of resource.

There is still a need for a safe, noninvasive, diagnostic modality that will allow stratification of cardiovascular risk among people with CKD. With the development of new imaging markers, it becomes difficult for clinicians to choose the imaging tests that can best aid clinical decisions for a given patient. Imaging methods should provide accuracy and precision at acceptable cost. Until advanced imaging techniques (e.g., cardiac MRI, positron emission tomography, cardiac computed tomography) are standardized, clinicians should rely on the most reliable and familiar techniques in their environment. 578

Clinical and cost-effectiveness could be improved; cardiac evaluation in people with CKD should be based on data from clinical trials.

If cardiac evaluation is at present predominantly used for risk stratification and prognosis, in the future it may guide optimal therapy and monitor clinical progress. 557

4.3 CKD AND PERIPHERAL ARTERIAL DISEASE

There is a strong link between CKD and peripheral arterial disease (PAD). Symptoms of PAD may only be present in a minority of people who have clinical evidence of PAD. 579 It is therefore important to measure ankle-brachial index and perform regular systematic assessment of the lower limbs of people at high risk of PAD to identify bruits, loss of pulses, cool pale extremities, delay in venous filling, and skin ulceration. 580 3.1: We recommend that adults with CKD be regularly examined for signs of peripheral arterial disease and be considered for usual approaches to therapy. (1B) 4.3.2: We suggest that adults with CKD and diabetes are offered regular podiatric assessment. (2A)

These statements are worded in this way in order to highlight the increased risk of PAD in people with CKD, particularly those with CKD and diabetes.

The prevalence of PAD is common in people with CKD and it increases with lower levels of GFR (Table 31 ). PAD can be [581] [582] [583] [584] [585] [586] [587] [588] Diabetes is the leading cause of CKD globally and the risk of diabetic foot ulceration and lower extremity amputation in subjects with diabetes increases dramatically with lower GFR. In a cohort of 90,617 individuals with diabetes over a median observation time of 2.4 years, the HR for amputation increased from 2.08 (95% CI 1.68-2.58) for those with GFR 30-59 ml/min/1.73 m 2 to 7.71 (95% CI 5. 29-11.26) for those with GFR o30 ml/min/1.73 m 2 compared to reference subjects with GFR 460 ml/min/1.73 m 2 . 589 creening for PAD is recommended for adults in the general population based on age and number of risk factors. 590 Although an ankle-brachial index of o0.9 is generally considered evidence of PAD, the utility of this measure is unproven in CKD because of the greater prevalence of vessel calcification. Evidence-based medical therapies for PAD in people with CKD are similarly lacking. Smoking cessation is mandatory. Aspirin may be beneficial for prevention of cardiovascular events. Clopidogrel has not been studied in people with CKD and PAD. No RCTs evaluating percutaneous versus surgical revascularization techniques have been conducted in people with CKD and PAD but outcome studies all suggest that CKD confers an increased risk of adverse outcome, regardless of the revascularization technique employed. 591, 592 These statements do not apply to pediatric practice.

There is no evidence to suggest that the international approach to identification and management of PAD in people with CKD should differ.

People with CKD are more at risk of PAD and need regular assessment and monitoring. The role of ankle-brachial index versus other diagnostic techniques may have implications for future practice. Prospective data on non-surgical therapies and data regarding percutaneous versus surgical revascularization are required to inform policy and recommended procedure.

There remains ongoing debate as to the timing and use of specific diagnostic criteria for identification of PAD in people with CKD and no studies have examined the utility of conventional methods in early detection of PAD in CKD. The use of specific medical and surgical management strategies in people with CKD and PAD has not been evaluated. There is no reason to believe that treatment strategies should differ, though risks of diagnostic testing (such as angiography) remain real.

4.4 MEDICATION MANAGEMENT AND PATIENT SAFETY IN CKD

Many drugs and investigative pharmaceuticals are renally excreted and their dosage may need to be reduced in patients with CKD in order to avoid toxicity. As many people with CKD are elderly, there should also be consideration of chronological age.

It is beyond the scope of this guideline to list all the agents that may need dose adjustment in CKD or which should be avoided due to potential nephrotoxicity. This information is widely available in documents which may exist at local, regional, or national bodies (e.g., British National Formulary: www.bnf.org), and other textbooks of pharmacology. 593, 594 However key classes of commonly prescribed drugs in people with CKD will be mentioned together with suggestions for dose adjustment. Much of this guidance is based upon our understanding of pharmacology and pharmacokinetics rather than randomized control trial evidence.

A cohort study by Lafrance et al. followed a referred CKD population in British Columbia for a median of 19.4 months after achieving a GFR of r30 ml/min/1.73 m 2 . Forty-five percent had at least one episode of AKI. 276 In another cohort study of 920,985 adults in Alberta, Canada with at least one outpatient measurement of SCr and proteinuria and not requiring chronic dialysis, risk of admission with AKI increased with heavier proteinuria and reduced GFR. 16 ternational Relevance

These guidelines about AKI have relevance around the world. While the causes of AKI may differ by region, country, socioeconomic status, and age, the consequences remain the similar. Where there are no facilitities to support AKI or CKD, people will die.

Interpretation of published data examining the influence of pre-existing CKD on the increased likelihood of AKI is potentially confounded by a number of issues. These include the comorbidities associated with CKD, influenced by repeated exposure to various nephrotoxic insults or inhospital errors, 57, 277 or primarily due to the altered physiology in CKD. There are also methodological issues such as how CKD and AKI are defined in clinical studies and the varying statistical adjustments for comorbidities which may affect the validity of observed associations.

A further important issue to clarify is whether pre-existing CKD influences the outcome of AKI. Currently, there is no single biomarker that can differentiate 'acute' from 'chronic' kidney disease and help to address this issue. 9] [280] [281] [282] [283] Data from PICARD reveal lower in-patient mortality and median length of stay in ICU subjects with acute-on-chronic renal injury compared with non-CKD subjects with AKI, though the post-discharge dialysis rates were higher in subjects with pre-existing CKD. 284

[655] [656] [657] [658]

Prospectively designed clinical studies with a clear and uniform definition of CKD and AKI and adjusted for comorbidities are needed to determine: K the frequency of AKI events in a CKD population K the outcome of AKI in patients with CKD condition

There are observational and database studies reporting an association between pre-existing CKD and hospitalizations and mortality. A better understanding of the rates, causes, and risk factors for hospitalization among people with CKD would allow estimates of the economic burden of CKD and identification of those at risk for increased resource utilization. People with CKD are an ideal target for interventions aimed at reduction of morbidity, hospitalization, mortality, and costs. These statements suggest that a coordinated approach to the identification and management would result in better outcomes and are intended as 'best practices' statements, recognizing the difficulty in developing an evidence base while addressing issues related to resource allocations (Table 34 ).

Mortality rates remain high (16-22%) with the use of dialysis, with more than half of all deaths related to CVD. Less is known about mortality and CVD rates, and resource use among persons with a reduced GFR who are not yet receiving maintenance dialysis. Few studies have investigated the association between CKD and the risk of hospitalization. Data from the USRDS reveal that hospitalization rates vary with comorbidity and interact with degrees of CKD. Adjusted rates are 38% higher in people with CKD and 19% greater in people with CKD and GFR under 60 ml/min/ 1.73 m 2 than in those with GFR 460 ml/min/1.73 m 2 , who in turn are 20% higher than in people without CKDillustrating the graded impact of advancing kidney disease. Not surprisingly, rates of cardiovascular hospitalization are greater for people with CKD, particularly those with increasing severity of CKD. 659 In both the CKD and non-CKD populations, adjusted rates of hospitalization increase with greater comorbidity. In 2008, for example, the rate for people with CKD with both diabetes and CHF was 726 per 1000 person-years at risk -85% greater than the rate of 393 among people with neither diagnosis. Rates of admission for CVD increase even more in the higher categories of GFR. Among Medicare subjects, the rate of 141 admissions per 1000 person-years for those with GFR o60 ml/min/1.73 m 2 is 26% higher than the rate of 112 reported for those with CKD and GFR Z60 ml/min/1.73 m 2 . The admission rates of 101 and 90 reported for MarketScan and Ingenix i3 subjects with GFR o60 ml/min/1.73 m 2 are 48 and 16% greater, respectively, than those occurring in people with higher GFRs. 633 Adjusted rates of mortality in USRDS 2008 increased with age, and were highest in people with advanced categories of GFR: 31-72% higher, for example, in people with GFR o60 ml/ min/1.73 m 2 compared to those with no CKD. By gender, rates in men with CKD were 91.8 per 1000 person-years at risk compared to 85.6 in women. Rates for people with CKD overall were similar in whites and African Americans, but in people with GFR o60 ml/min/1.73 m 2 , rates for African Americans were 18% higher than those for whites, at 95.0 and 80.5 per 1000 person-years, respectively. 633 han et al. 660 confirmed that hospital utilization among people with CKD is high. During a median follow-up of 11.4 months, 47% of subjects had at least one hospitalization and there were on average 0.96 hospitalizations, 6.6 hospital days, and 4.0 outpatient nephrology visits per person-year at risk. Cardiac disease/hypertension was the most common primary diagnosis of hospitalizations and progression of CKD/acute kidney failure was the most common secondary cause of hospitalization. The authors had previously shown that the dialysis population at their institution had 2.2 hospitalizations and 14.8 hospital days per person-year at risk, 659 which was similar to that among US hemodialysis patients between 1996 and 1998, who had 1.9 hospitalizations and 14 hospital days per person-year at risk. 661 In the general population, there were 0.31 hospitalizations and 1.9 hospital days per person in 1998. 662 o et al. 58 reported an independent, graded association between GFR and the risk of death, cardiovascular events, and hospitalization in 1,120,295 adults within a large, integrated system of health-care delivery in whom SCr had been measured between 1996 and 2000 and who had not undergone dialysis or kidney transplantation. These risks were evident at GFR o60 ml/min/1.73 m 2 and substantially increased at GFR o45 ml/min/1.73 m 2 .

The higher hospital utilization among people with CKD compared to the general population, and the similarity in the comorbid conditions and the causes of hospitalization between people with CKD and ESRD, confirm the hypothesis that the complications and comorbidity observed in ESRD are manifest earlier in the disease process. Previous studies have demonstrated an association between age, gender, race, cardiac disease, peripheral vascular disease, serum albumin and hematocrit levels, and resource utilization among people on dialysis. 659, 663, 664 Holland et al. 665 identified baseline predictors of first non-elective hospitalization among a retrospective cohort of 362 predialysis subjects. Multivariate analysis, adjusted for baseline creatinine concentration, selected advanced age (RR 1.02; 95% CI 1.01-1.03), angina (RR 1.9; CI 1.37-2.61), peripheral vascular disease (RR 1.55, CI 1.05-2.27), and Hb concentration (RR 0.99, CI 0.94-0.98) as independent predictors of hospitalization. These comorbid conditions progressively worsen with advancing kidney disease and result in a substantial proportion of people having severe complications by the time they come to RRT.

Interventions to reduce hospitalizations and mortality for people with CKD should pay close attention to the management of associated comorbid conditions and CVD. 666 Closer attention to the management of heart disease in this population could substantially improve outcomes. 667 he influence of correction of anemia on hospitalization is controversial. Dru ¨eke et al. 668 randomly assigned 603 subjects with GFR 15-35 ml/min/1.73 m 2 and mild-to-moderate anemia (Hb level: 11.0-12.5 g/dl [110-125 g/l]) to a target Hb value in the normal range (13.0-15.0 g/dl [130-150 g/l]) or the subnormal range (10.5-11.5 g/dl [105-115 g/l] ). There were no significant differences between the two groups in the incidence of hospital admission (61% and 59%, respectively) or mean duration of hospitalization for cardiovascular reasons (33.0 and 28.2 days, respectively). Singh et al. 669 studied 1432 people with CKD, 715 of whom were randomly assigned to receive a dose of epoetin alfa targeted to achieve a Hb level of 13.5 g/dl (135 g/l) and 717 of whom were assigned to receive a dose targeted to achieve a level of 11.3 g/dl (113 g/l). The median study duration was 16 months. The primary end point was a composite of death, MI, hospitalization for CHF (without RRT), and stroke. They observed an increased risk of the primary composite end point in the high Hb group as compared with the low Hb group. Death and hospitalization for CHF accounted for 74.8% of the composite events. The Trial to Reduce Cardiovascular Events with Aranesp Therapy (TREAT) 375 study involved 4038 people with diabetes, CKD, and anemia. Subjects were randomly assigned to treatment with darbepoetin alfa to achieve a Hb level of approximately 13 g/dl (130 g/l) or to placebo, with rescue darbepoetin alfa when the Hb level was less than 9.0 g/dl (90 g/l). The primary end points were the composite outcomes of death or a cardiovascular event (nonfatal MI, CHF, stroke, or hospitalization for myocardial ischemia) and of death or ESRD. Again there were no significant between-group differences in the outcomes of interest.

It is of benefit for all jurisdictions to appreciate the increase in resource utilization by CKD populations. Identification of people at risk for increased resource utilization and economic burden of CKD should result in strategies to attenuate that risk or address the resource implications. Selection of interventions that could reduce hospitalizations, morbidity, mortality, and costs in these populations should be evaluated.

While every effort is made by the publishers, editorial board, and ISN to see that no inaccurate or misleading data, opinion or statement appears in this Journal, they wish to make it clear that the data and opinions appearing in the articles and advertisements herein are the responsibility of the contributor, copyright holder, or advertiser concerned. Accordingly, the publishers and the ISN, the editorial board and their respective employers, office and agents accept no liability whatsoever for the consequences of any such inaccurate or misleading data, opinion or statement. While every effort is made to ensure that drug doses and other quantities are presented accurately, readers are advised that new methods and techniques involving drug usage, and described within this Journal, should only be followed in conjunction with the drug manufacturer's own published literature. Early identification and referral of people with CKD has the potential to reverse, delay, or prevent progression of disease and is a key focus of international initiatives in the area of kidney disease. The goals of early identification and referral are several-fold and include:

This statement reminds the practitioner that there is a need for timely referral for RRT planning in order to ensure good decision making and outcomes. The use of the word 'timely' is vague as this is not yet determined, and is based on patient and system factors. The actual amount of time required at a minimum is at least 1 year to ensure appropriate education, understanding and referrals to other practitioners (e.g., vascular access surgeons, transplant teams, etc). The second part of the statement refers to the fact that those who are progressing (versus those who are stable) are the ones who will benefit from this referral. Hence, there is a need to apply prediction tools to help identify the risk of progression. We have not stated which prediction tool is preferred as these may differ depending on information available in any individual or local experience. Examples of prediction tools can be found in recent publications. 257, 260, 261 he scope of nephrology practice includes a wide variety of conditions including not only ESRD but also acute and chronic primary and systemic diseases involving individual elements of the kidney, resistant hypertension, and biochemical derangements. There are thus more potential benefits of nephrology referral than those widely recognized such as identification of reversible causes of CKD, provision of treatment that may slow progression of CKD, management of the metabolic complications of advanced CKD, and preparation for dialysis and transplantation.

In certain people, such as those with diabetes, transition to a severe reduction in GFR and kidney failure may progress rapidly. In such individuals early nephrology referral is the watchword but when an individual's kidney function is relatively stable (rate of decline in GFR o5 ml/min/1.73 m 2 /year), we suggest using the grid as a guide (Figure 21 ). Where refer is marked by an asterisk, referring clinicians may wish to discuss with their nephrology service depending on local arrangements.

Although referral recommendations in the literature are inconsistent, criteria for nephrology referral include SCr or GFR, proteinuria, hematuria, BP, and electrolyte derange-c h a p t e r 5 http://www.kidney-international.org & 2013 KDIGO *If this is a stable isolated finding, formal referral (i.e., formal consultation and ongoing care management) may not be necessary and advice from specialist services may be all that is required to facilitate best care for the patients. This will be health-care system dependent. w The aim is to avoid late referral, defined here as referral to specialist services less than 1 year before start of RRT. ment. 670 Data relating to referral for those with glomerular disease, hypertension, AKI, and diabetes may be found in the relevant guidelines. 7, 8, 10, 262 n this section we will briefly consider summaries of the evidence relating to timely referral for planning RRT in people with progressive CKD. In this aspect the literature concerning late referral in the last quarter of a century has been remarkably consistent; both studies and narrative reviews identifying a number of adverse consequences of late referral and related benefits of early referral (Table 35 ).

Patients who are aged 475 years, female, non-Caucasian, uninsured, of lower socioeconomic or educational status, or have multiple comorbidities are most at risk for non-referral for CKD care. 671, 672 Patients with kidney disease have never been randomized to early or late referral to nephrology services and the definition of late referral in the published studies varies; three months is probably less than the absolute minimum amount of time required for assessment, education, preparation for RRT and creation of access but is the most frequently employed definition. Overall there are more than 50 studies in the published literature and a meta-analysis of 22 of these studies from 10 different countries serves to underline some of the key messages (Table 36 ), giving an indication of the size of the differences in mortality and hospital length of stay and also highlighting the significantly lower serum albumin level in late referred patients. 673 systematic review considered twenty-seven longitudinal cohort studies providing data on 17,646 participants of whom 11,734 were referred early and 5912 (33%) were referred late. 674 OR for mortality reductions in patients referred early were evident at 3 months (OR 0.51; 95% CI 0.44-0.59; Po0.0001) and remained significant at 5 years (OR 0.45; 95% CI 0.38-0.53; Po0.0001). Initial hospitalization was 8.8 days shorter with early referral (95% CI -10.7 to -7.0 days; Po0.0001). Differences in mortality and hospitalization data between the 2 groups were not explained by differences in prevalence of diabetes mellitus, previous CAD, BP control, serum phosphate, and serum albumin. Early referral was associated with better preparation and earlier placement of dialysis access and better uptake of peritoneal dialysis.

Over a decade ago McLaughlin et al. evaluated the cost implications of early versus late referral. 675 Outcomes of interest were total cost of patient care, patient life-years, patient life-years free of RRT and hospital length of stay. Mean total costs per patient over five years were US$87,711 and US$110,056 for early and late referrals, respectively. The mean patient life-years were 3.53 and 3.36 years, respectively, and the patient life-years free of RRT were 2.18 and 1.76 years, respectively. Those patients referred early spent significantly less time in hospital (length of stay 25 days versus 41 days). Klebe et al. subsequently investigated the annualized cost of implementation of referral guidelines for CKD. 676 Although CKD guideline implementation resulted in significant increases in nephrology referral and additional investigation, they estimated that the associated costs could

Local practice and resource will dictate local referral practice but regardless of the health-care system, delay or prevention of progression of both CKD and complications associated with CKD will add value. Local organizations will determine the best methods of communication and interaction between patients, specialists, and primary care physicians.

Implementation of referral guidelines will inevitably lead to an increased workload for specialist nephrology services. However, introduction of local initiatives in conjunction with primary care providers can improve the appropriateness and quality of the referral. Local initiatives combined with national policy and practice changes can lead to an improvement in the outcomes of CKD patients regardless of the level of resource available.

Current pediatric practice in most areas of the world would suggest a higher level of kidney function for referral than that for adults, though the principles remain the same. Much of the pediatric nephrologist's consultation occurs from infants, or even antenatal sources, where the identification of the child as being 'at-risk' may be apparent from radiographic studies performed in utero. The relatively non-specific signs and symptoms of most forms of renal disease in the young child mandates a higher level of suspicion in the referring physician, and a lower threshold of acceptance of the consult in the subspecialty clinic accepting these referrals. Attempts to develop universal guidelines for referral of children to pediatric nephrology services would be dependent on local resources (as is the case for adults) and it is of value to consider in broad categories the types of conditions for which referral to a pediatric nephrologist would be expected to provide benefit to the referring physician and patient/family.

In a recent review Barakat 677 attempts to address a number of these issues by outlining the most common presentations of a child with significant renal disorders. Barakat and Chesney also suggest a number of specific areas in terms of initial investigations, management, and follow-up where the primary care physician can legitimately play a role in the care of the child with renal disease and provides a list of suggested referral triggers. 678 hile there will be variation in referral triggers, referral would be recommended for the following: acute or chronic reduction in renal function, poorly treated or severe hypertension, severe electrolyte abnormalities, the finding of significant abnormalities in urinary tract structure, or the presence of systemic diseases likely to produce renal effects. Similarly, the need for education in progressive conditions, performance of and interpretation of renal biopsies, and allaying parental/patient anxiety would also be acceptable reasons for referral.

There is no 'minimum acceptable value' of renal dysfunction below which one can be certain to see significant abnormalities in clearance, electrolyte, or other side effects associated with progressive renal disease in children such as growth failure or neurocognitive issues. However, the c h a p t e r 5 KDOQI CKD Guidelines 1 stated that while a child with a eGFR o30 ml/min/1.73 m 2 warranted referral to a pediatric nephrologist in all cases, that in fact it was also reasonable to consider any child with evidence of CKD-and in particular those with eGFR o60 ml/min/1.73 m 2 -for referral to a pediatric nephrologist regarding evaluation and management. 43 t is reasonable to presume that, as in adults, the concept of referral 'early' or 'above' some minimum level of function should allow for numerous benefits to the patient and family, but again there are few data for this in children. The most informative information on both of these issues can be derived from two papers examining the issue of late referrals of children who eventually required ESRD care. Kennedy et al. 679 demonstrated that at the time of referral to their center, the children 41 year of age had a median Schwartz eGFR of only 27 (IQR 9-52) ml/min/1.73 m 2 , and in fact 55% of these children over the age of 1 year were referred with an eGFR o30 ml/min/1.73 m 2 , meeting one of two definitions of a late referral. When they considered their second definition of initiation of RRT within 90 days of referral, commonly used in the literature for this particular topic, 30% of the eligible cohort required RRT within that 90-day window and hence were considered late referrals on this basis. The potential effect on the child's health could be ascribed to such a delay in referral: those children had lower mean Hb (8.7 ± 0.6 g/dl [87 ± 6 g/l]) versus (12.8 ± 0.6 g/dl [128 ± 6 g/l] ) and higher median urea (34 (IQR 5-14) mmol/l [203 (IQR 30-84) mg/dl] versus 6 (IQR 5-14) mmol/l [36 (IQR 30-84) mg/dl] , Po0.001) than those who presented with eGFR 430 ml/min/1.73 m 2 . Secondary analysis confirmed this was also true in the groups if one looked at those above or below an eGFR of 60 ml/min/ 1.73 m 2 . The second paper by Boehm and colleagues 680 was a retrospective single pediatric center report that demonstrated that over B30 years of referrals (N ¼ 111), 24% of them could be considered as late referrals, as defined by need for RRT within 90 days of referral. In this late referral group, the eGFR (Schwartz) was significantly lower than those presenting later, (14.9 versus 34.2 ml/min/1.73 m 2 , Po0.001) as was the Hb at presentation (8.0 g/dl [80 g/l] versus 10.5 ± 2.3 g/ dl [105 ± 23 g/l] ; Po0.001). Importantly the Hb deficit persisted at the time of RRT initiation, with the Hb in the late referral group being 8.5 g/dl [85 g/l] versus 9.8 ± 1.9 g/dl [98 ± 19 g/l] in the earlier referred patients, Po0.01. The other metric of interest chosen by these authors to evaluate the possible detrimental effect of late referral was the likelihood of a given child having a pre-emptive transplant, i.e., prior to dialysis initiation. While this association was not confirmed in Kennedy's paper, Boehm and his group demonstrated that in their patient population children who were referred late only 11% were preemptively transplanted as compared to 40% of children who presented to care more than 90 days prior to the need for some form of RRT. Of further interest, although somewhat counterintuitive, the proportion of patients in the Boehm study who initiated hemodialysis was not statistically different between those in the late versus early referral groups, 62% versus 67%, Po0.05 respectively.

The underlying concept of referral to a pediatric nephrologist in the face of rapid progression of renal failure is of course applicable in full. However, no current validated risk of progression tool exists in pediatric nephrology. As to what level of functional decline might be considered 'concerning,' the best evidence is derived from the longitudinal iohexol GFR data as accrued in the CKiD trial. Data from that study related to the annualized rate of decline in renal function for children with glomerular conditions is À10.5% as compared to those with a non-glomerular causes in whom the annualized rate of change is only À3.9%. 71 Any child whose rate of decline exceeded these two values would at least warrant much closer follow-up and/or investigation for modifiable factors to slow progression. Note this is not to say these rates of decline should be considered to be 'normal' for either category. All efforts to slow decline in renal function would still be of vital importance in every individual.

5.2: CARE OF THE PATIENT WITH PROGRESSIVE CKD

The following section describes recommended structures and key milestones for people with progressive CKD. The recommendations are intended to model best practices but it is appreciated that different health-care systems, geographical issues, and economic considerations will have variable abilities to implement these recommendations.

Key aspects of caring for people with progressive CKD, as they approach end of life or RRT options are addressed in this section.

5.2.1:

Standardized and culturally appropriate protocols should be considered. While it is recognized that resources may vary across and within jurisdictions, recommendations here are based on principles of care, which should be relevant across the globe.

CKD is a complex condition and co-exists with many other conditions. Therefore models of care should be developed that integrate the complexity of the clinical conditions involved, patient-centered philosophies, and the health-care environment. The principles of care are universal but implementation may be customized to specific circumstances.

Papers addressing the need for and effectiveness in the utility of multidisciplinary clinics for management of pediatric CKD patients have been published. In 2012, Ajarmeh et al. 682 described a retrospective comparison of two cohorts of children aged 0-18 years of age and followed at a single Canadian tertiary care referral center over a 1-year time period either before or following the full implementation of a multidisciplinary CKD clinic which included the services of dedicated pediatric nephrologists, renal nursing, pharmacy, dietitians, social workers, and a renal database manager. In 2009, Menon et al. 683 published data from a large American pediatric referral center and compared the outcomes of children from one of two 5-year cohorts in the period immediately preceding or following the initiation of a specific Chronic Renal Insufficiency clinic which was staffed by pediatric nephrologists, nurse clinicians, transplant coordinators, dietitians, social workers, and a psychologist. Ajarmeh et al. 682 compared the two cohorts in a number of areas during their year of follow-up whereas Menon et al. 683 chose to look at each individual patient in the 12 months immediately prior to initiating RRT. While the studies had different variables of interest and used slightly different approaches for comparison of results between their groups, both demonstrated a reduction in the rate of decline in estimated renal function, improved Hb levels, and improvement in at least some aspect of bone mineral metabolism control in their respective cohorts cared for in the multidisciplinary era. In addition, both studies also demonstrated a decrease in resource utilization by patients in the multidisciplinary clinic as measured by median length of stay 682 and number of unplanned admissions per patient per year. 683 Also of note, Menon et al. demonstrated that in the patients who initiated dialysis (which was how the cohort was chosen), more patients who started hemodialysis did so with a functioning arteriovenous fistula or arteriovenous graft at the time of initiation compared to those from the general nephrology clinic era (85.7 versus 20%, P ¼ 0.02).

5.3: TIMING THE INITIATION OF RRT

5.3.1:

We suggest that dialysis be initiated when one or more of the following are present: symptoms or signs attributable to kidney failure (serositis, acidbase or electrolyte abnormalities, pruritus); inability to control volume status or blood pressure; a progressive deterioration in nutritional status refractory to dietary intervention; or cognitive impairment. This often but not invariably occurs in the GFR range between 5 and 10 ml/min/1.73 m 2 . (2B) 5.3.2: Living donor preemptive renal transplantation in adults should be considered when the GFR is o20 ml/min/1.73 m 2 , and there is evidence of progressive and irreversible CKD over the preceding 6-12 months. (Not Graded)

The statement is worded very precisely to highlight the need for RRT to address symptoms and to avoid the institution of dialysis therapy at an arbitrary number representing the degree of residual renal function. Given the risks and benefits of RRT, as well as the potential imprecision of measurements, patients need to be treated according to symptoms and signs, not simply based on a laboratory value. Data from national registries has shown a consistent rise in GFR at initiation of RRT. This rise has been driven partly by a desire to improve nutritional status and also by earlier observational data suggesting adverse outcomes associated with RRT initiation at lower GFR. These early data were subject to much confounding. RCT data, supported by large registry-based studies corrected for confounding, show no survival advantage to early start dialysis (Initiating Dialysis Early and Late [IDEAL] study, see Evidence Base Below). Thus, the statement as written should help the clinician to balance symptoms with laboratory values in decision making.

The statement regarding living donor transplantation is intended to ensure that practitioners think about this option in the context of the totality of RRT options. It is worded to be concordant with local living donation transplant policies. It aims to reflect the need for risk-benefit assessment of preemptive renal transplantation in all individuals. Note that the statement asks clinicians to consider this option, but does not state at which level of GFR the preemptive transplant would occur as this is a matter of local practice and patientspecific considerations.

The perceived survival advantage of early start of dialysis was questioned by a study from the Netherlands Cooperative Study on the Adequacy of Dialysis Study Group (NECO-SAD). 684 Of 253 patients with new ESRD, 94 (37%) started dialysis late (GFR 4.9 ± 1.7 ml/min/1.73 m 2 ) and 157 started in a timely fashion (GFR 7.1 ± 2.4 ml/min/1.73 m 2 ). Although there was a small gain in survival time over 3 years after start of dialysis for the timely start group (2.5 months) there was no significant difference in survival between the 2 groups and the gain in survival time was offset by an estimated lead-time bias of between 4.1 and 8.3 months. In a study eliminating the effect of lead-time bias Traynor et al. found no benefit in survival in those initiating dialysis early. 685 Subjects starting dialysis early (N ¼ 119) had a median IQR CrCl of 10.4 (9.1-11.9) ml/min versus 6.7 (5.6-7.5) ml/min in 116 subjects starting dialysis late. After correction for multiple confounders, they found an 11% greater hazard for mortality with each 1 ml/min increase in CrCl at start of dialysis (HR 1.11; 95% CI 1.01-1.21; P ¼ 0.024). 7] [688] [689] [690] [691] [692] [693] [694] [695] [696] These studies encountered multiple difficulties in drawing conclusions from this observational approach including lead-time bias, problems with estimating GFR from SCr in people with low muscle mass and/or fluid overload, the fact that people with symptoms and/or increased comorbidity are more likely to start dialysis early, and finally survivor bias in studies including people only when they start dialysis (and therefore excluding those who die prior to starting diaysis). These confounders were largely addressed by a multicenter controlled trial in which 828 adults with progressive CKD and CrCl 10-15 ml/min/1.73 m 2 were randomly assigned to early (CrCl 10-14 ml/min [0.17-0.23 ml/s]) or late (CrCl 5-7 ml/min [0.08-0.12 ml/s]) initiation of dialysis. 697 The study protocol allowed an earlier start where deemed clinically necessary by investigators and although the difference in GFR at dialysis initiation between the 2 groups was significant (early start CrCl 12.0 versus late start 9.8 ml/min, MDRD GFR 9.0 versus 7.2 ml/min/ 1.73 m 2 ), it was less than planned because 19% of early starters started late and 76% of late starters started early. There was no difference in mortality between the early and late start groups and no difference in the study's secondary outcomes (cardiovascular events, infectious events and complications of dialysis) between the 2 groups. Finally, a further observational study sought to examine the effect of early initiation of dialysis on survival in a 'healthy' group of 81,176 subjects with ESRD aged 20-64 years, without diabetes, and with no comorbidity other than hypertension. 698 The unadjusted 1-year mortality by MDRD GFR at dialysis initiation ranged from 6.8% in the reference group (GFR o5.0 ml/min/1.73 m 2 ) to 20.1% in the highest GFR group (Z15.0 ml/min/1.73 m 2 ). In an even healthier subset of 35,665 subjects with serum albumin concentrations of 3.5 g/dl or higher prior to hemodialysis initiation, the 1-year mortality was 4.7%. In this group the adjusted HR for mortality was 1.27 for GFR 5.0-9.9 ml/min/ 1.73 m 2 , 1.53 for GFR 10.0-14.9 ml/min/1.73 m 2 , and 2.18 for GFR Z15.0 ml/min/1.73 m 2 compared with the reference group of GFR o5.0 ml/min/1.73 m 2 .

The availability of resources for formal multidisciplinary teams, educational materials, and access to specialized counseling for diet, advance directives, access planning, and pre-emptive transplantation varies around the world. These statements are proposed so that 'best practices' can be documented or aspired to. The need for education, planning, and appropriate expertise for the management of this patient group is internationally relevant. The methods, frequency, and tools with which this can be accomplished will be region specific.

There is a need to focus on regular symptom assessment as part of CKD review in those with lower eGFR values. Individual assessment and availability of resources will dictate specific timing of therapies.

Clinicians should be aware of the impact of early dialysis start on QOL 699 before recommending this strategy to patients.

Pediatric Consideration

Timing of initiation of dialysis. As might be expected, information as to the proper timing for initiation of dialysis does not exist for children. Thus, it would seem reasonable to follow the guidelines as set out for the adults. A review by Greenbaum and Schaefer 700 provides the reader with generally agreed upon absolute and relative indications for initiation of dialysis in the child. The absolute indications listed are those of neurologic consequences attributable to uremia; hypertension that fails to respond to antihypertensive therapy; pulmonary edema unresponsive to diuretics; pericarditis; bleeding tendency; and refractory nausea or vomiting. However, the authors clearly state that there is no current consensus as to the validity of the relative indications and specifically the level at which each engenders the need for dialysis. Relative indications to commence dialysis include less severe uremic symptoms, hyperkalemia, hyperphosphatemia, malnutrition, and growth failure. The authors point out as well that the answer to 'early' versus 'late' dialysis initiation cannot be addressed in any meaningful way in children as there is currently lack of data; and the unique factors to consider in a child such as growth, psychosocial development, likely renal transplant, and need for extended time on both dialysis and in transplant make the probability of a clinical trial to address this issue nearly impossible.

Timing of living donor transplant. There is no direct evidence to guide the pediatric nephrologist as to the 'best' timing for a living donor transplant in children. In each individual case the relative likelihood of improvement in presumed uremic symptoms and burden of disease as related to management of CKD will need to be balanced against the risks of transplant surgery itself and the attendant medication risks with prolonged immunosuppression. While there is little doubt as to the benefit in overall lifespan accrued by a child who is transplanted as opposed to one maintained on standard dialysis therapies during their childhood (average life expectancy of 63 versus 38 years respectively), 701 the issue as to what level of residual function is sufficient to justify delay or conversely proceeding to transplant is simply not readily available.

It should also be noted that reliance on GFR as the sole marker of disease intensity is unlikely to be sufficient for making such a decision, and patient symptoms and/or unique family factors may play a significant role in the decision as to timing of a living donor transplant (e.g., a young grandparent available and healthy to donate at age 60 years may not be eligible at age 63 years and so an earlier transplant would be favored). program should include protocols for symptom and pain management, psychological care, spiritual care, and culturally sensitive care for the dying patient and their family (whether at home, in a hospice or a hospital setting), followed by the provision of culturally appropriate bereavement support. (Not Graded)

These statements are intended to highlight the need for comprehensive conservative care processes and resources in the care of this complex patient group. There is increasing recognition that provision of organized care to those who are dying or choose to not pursue dialysis and transplant care is of value to the patients and their families. Clinicians involved in caring for these patients should be alerted to this need. These statements are positioned so as to overtly state this need.

In different societies or cultural areas, the form and structure of this care may vary tremendously and families or religious organizations may be able to deliver expert and sensitive care. The details here are listed not to be prescriptive but rather to articulate the 'best practices' in communities where resources may be available and to serve a construct to review in those locations where resources are more limited.

The evidence base for these statements is limited to documents describing the burden of illness and unmet needs in patients with CKD as they decide either not to pursue dialysis or to withdraw from RRT. As the readers will appreciate, there are neither RCTs nor even large cohort studies to inform these statements within the CKD populations. Analogies with oncology have been drawn and literature from there has been used to justify the concepts above.

Patients with advanced CKD have extensive palliative care needs for years before death. 3] [704] [705] [706] [707] The number and severity of physical and emotional symptoms are similar to those of cancer patients hospitalized in palliative care settings. 703, 708 Advanced CKD patients managed without dialysis are equally symptomatic. 706 An increasing number of dialysis patients die after withdrawal of dialysis (10-15% in 1990, 20% in 2004), primarily due to poor QOL, representing the second leading cause of death after CVD.

Conservative care focuses on slowing the decline in renal function, actively managing symptoms, advance care planning, and the provision of appropriate palliative care. In oncology, receiving early palliative care is associated with better QOL, fewer emergency department visits and hospitalizations, less aggressive care at the end of life, and surprisingly, longer survival. 709 These observations suggest that development of clinical models that integrate appropriate palliative care, including the creation of conservative care pathways, are likely to be hugely beneficial and would help avoid harmful dialysis to those patients unlikely to realize benefit. Such conservative care programs are slowly being developed, primarily in the UK and Canada. ] [711] [712] [713] [714] [715] [716] Poor quality, hospitalized deaths began to improve for patients dying with cancer as a result of an increasing emphasis on palliative care teams providing attention to symptom control, psychosocial needs, and options for location of care. The literature suggests that current models of palliative care for cancer patients that deinstitutionalized health-care services have not only improved patient outcomes and quality of care [717] [718] [719] [720] but have been costneutral. 721

All countries have people with CKD who withdraw either voluntarily or involuntarily from dialysis services. Best care for those patients will obviously need to respect cultural and religious values, but would necessarily be based on the same philosophical grounds of maintaining dignity of the individual. Appreciating the need for and articulating conservative care pathways overtly would be internationally applicable.

There is a need to ensure appropriate access to services and education surrounding quality care during terminal stages of a chronic condition. There is increasing attention to this in many societies but not in all. Appreciating the variability in the resources required and their availability to different groups of patients is important for implementation. Furthermore, involvement of religious and cultural leaders in recognition of these care practices can be enhanced if they are overtly recognized as part of the care continuum.

There is a need for robust assessment of best practices in CKD and other chronic conditions so that we may provide best care throughout the continuum of life. Researchers around the world are actively pursuing this so that we may have better tools, programs, and ultimately, better outcomes for our patients.

Despite the lack of published evidence, there is no reason to believe that children and families faced with the need to consider conservative care or a palliative approach to their impending ESRD would not benefit from all of the above recommendations. It would seem reasonable for pediatric nephrology centers to liaise with their pediatric oncology or palliative care teams, ethicists, and pastoral care providers to assist them in developing, defining, and/or identifying locally available resources for situations where a child is not deemed a candidate for RRT prior to their occurrence.

AIM

The overall aim of this project was to develop an evidencebased clinical practice guideline for evaluation and management of CKD. The guideline consists of recommendation statements, rationales, and a summary of systematically generated evidence on relevant pre-defined clinical topics. To a large extent the guideline builds on the output of the KDIGO Controversies Conference in 2009, 30 which generated epidemiological data to support a revision of the classification and staging system. The vision for this KDIGO guideline is that it would endorse the current CKD definition as an imperfect convention for describing a state of function, revise classification based on risk, revise risk states, and revise and update action plans in view of the revised classifications. Additional systematic evidence review focused on specific topics.

OVERVIEW PROCESS

The guideline development process included the following steps: Throughout the project, the ERT offered suggestions for guideline development and led discussions on systematic review, literature searches, data extraction, assessment of quality and applicability of articles, evidence synthesis, grading of evidence and guideline recommendations, and consensus development. The Work Group took the primary role of writing the recommendation statements and rationales and retained final responsibility for their content.

Defining Scope and Topics

This KDIGO CKD guideline was set out to update the KDOQI Clinical Practice Guidelines for CKD: Evaluation, Classification, and Stratification 1 in 2002, which spans many topics related to the diagnosis, classification, stratification, and management of CKD. 1 The Work Group Co-Chairs prepared the first draft of the scope of work document as a series of open-ended questions to be considered by Work Group members. At their first 2day meeting, members added further questions until the initial working document included all topics of interest to the Work Group. The inclusive, combined set of questions formed the basis for the deliberation and discussion that followed. The Work Group strove to ensure that all topics deemed clinically relevant and worthy of review were identified and addressed.

Updating the topics of definitions and classification was based on the output from the KDIGO Controversies Conference and the CKD Prognosis Consortium. 4, 30 dditional topics that relate to explicit selection of diagnostic tests or interventions were chosen to undergo systematic review of the best available evidence. Systematic evidence review entails a priori question formulation, specification of important outcomes for the review, systematic searches, data extraction, tabulation, analysis, and synthesis of evidence and is described in detail for each of the specific questions. The process followed for each evidence review topic (a total of four non-treatment topics and four treatment topics) is detailed below.

The eight topics for which the ERT conducted searches and evidence review are shown in Table 37 . For the systematic review topics, the Work Group and ERT further developed and refined each topic and specified screening criteria, literature search strategies, and data extraction forms.

Many other topics were not suitable to be addressed by indepth evidence review. When the anticipated outcome of an extensive literature search was unlikely to yield evidence that directly informs practice choices, the approach chosen was that of a narrative review.

APPROACH TO EVIDENCE REVIEW TOPICS Formulating Questions of Interest

Questions of interest were formulated according to the PICODD (Population, Intervention or Predictor, Comparator, Outcome, study Design, and Duration of follow-up) criteria. Details of the PICODD criteria are presented in Table 37 .

Literature Searches and Article Selection for Evidence Review Topics

Search strategies were developed by the ERT, with input from the Work Group, for each topic of interest (whether treatment or non-treatment topics). The ERT performed literature searches and conducted abstract and article screening. The ERT also coordinated the methodological and analytic processes, data extraction, and summarizing of the evidence. Before initiating our own de novo systematic review, we searched for existing systematic reviews that could be used. The searches and search terms are provided in Supplemental Table 1 and the search dates and yields for all topics are presented in Table 38 .

Selection of Outcomes of Interest

The Work Group selected outcomes of interest on the basis of their importance for informing clinical decision making. Importance of mortality and ESRD was considered to be critical; the importance of progression of CKD and categorical or continuous measures of kidney function was considered to be high; and the importance of QOL, BP, gout attacks, and proteinuria was considered to be moderate.

Data Extraction

Text articles were extracted by the ERT onto forms customized to capture data on design, methodology, baseline characteristics, interventions or predictors, comparators, outcomes, results, and limitations of individual studies. Study methodology and risk of bias were also systematically graded for each outcome and recorded.

Summary Tables

Pertinent information for systematic review topics was tabulated in summary tables. Summary tables list outcomes of interest as well as relevant population characteristics, descriptions of interventions and comparators, results, and quality grades for each outcome. Categorical and continuous outcomes were summarized separately. Work Group members reviewed all summary table data and quality grades.

Evidence Profiles

Evidence profiles are usually constructed as a means to assess the quality and record quality grades and descriptions of effect for each outcome across studies, as well as the quality grades and description of net benefits or harms of the intervention or comparator across studies. These profiles aim to make the evidence synthesis process transparent. However, since no treatment or non-treatment topic had more than one study in a summary table for which the quality was graded, no evidence profiles were generated, and the information in the summary table shows the highest level of synthesis.

Grading of Quality of Evidence for Outcomes of Individual Studies

Methodological quality. Methodological quality (internal validity) refers to the design, conduct, and reporting of outcomes of a clinical study. A previously devised three-level classification system for quality assessment was used to grade the overall study quality and quality of all relevant outcomes in the study (Table 39 ). Variations of this system have been used in most KDOQI and all KDIGO guidelines and have been recommended for the US Agency for Healthcare Research and Quality Evidence-based Practice Center program. 722 ach study was given an overall quality grade on the basis of its design, methodology (randomization, allocation, blinding, definition of outcomes, appropriate use of statistical methods, etc.), conduct (drop-out percentage, outcome assessment methodologies, etc.), and reporting (internal consistency, clarity, thoroughness, and precision, etc.). Each reported outcome was then evaluated and given an individual grade depending on the quality of reporting and methodological issues specific to that outcome. However, the quality grade of an individual outcome could not exceed the quality grade for the overall study.

Grading the Quality of Evidence and the Strength of Guideline Recommendations

A structured approach, based on the GRADE approach, [723] [724] [725] was used to grade the quality of the overall evidence and the strength of recommendations for each topic. This grading scheme-with two levels for the strength of a recommendation together with four levels of grading for the quality of the evidence, as well as the option of an ungraded statement for general guidance-was adopted by the KDIGO Board in December 2008. The strength of a recommendation indicates the extent to which one can be confident that adherence to the recommendation will do more good than harm. The quality of a body of evidence refers to the extent to which our confidence in an estimate of effect is sufficient to support a particular recommendation. 724 The process of transparently grading evidence and recommendations for treatment topics is described below in further detail. However, the approach had to be adapted for the main topics of the KDIGO CKD guideline because they were not treatment-related topics.

Grading the Quality of Evidence for Each Outcome Across Studies

Following the GRADE approach, the quality of a body of evidence pertaining to a particular outcome of interest was initially categorized on the basis of study design (Table 40 ). For questions of interventions, the initial quality grade was high if the body of evidence consisted of RCTs, low if it consisted of observational studies, and very low if it consisted of studies of other designs. For questions of interventions, the Work Group decided to use only RCTs. The grade for the quality of evidence for each intervention-outcome pair was then lowered if there were serious limitations to the methodological quality of the aggregate of studies, if there was thought to be a high likelihood of bias, if there were important inconsistencies in the results across studies, if there was uncertainty about the directness of evidence (including limited applicability of the findings to the population of interest), if the data were sparse (for example if there was only one study or if the results include just a few events or observations and were uninformative) or imprecise (for example the CI spans a range greater than 1 or confidence limits are o0.5 to 42.0). The final grade for the quality of the evidence for an intervention-outcome pair was then assigned as high, moderate, low, or very low (Table 40 ).

Grading the Overall Quality of Evidence

The quality of the overall body of evidence was then determined on the basis of the quality grades for all outcomes of interest, taking into account explicit judgments about the relative importance of each outcome. The resulting four final categories for the quality of overall evidence were A, B, C, and D (Table 41 ).

Assessment of the Net Health Benefit Across All Important Clinical Outcomes

The net health benefit was determined on the basis of the anticipated balance of benefits and harms across all clinically important outcomes (Table 42 ). The assessment of net benefit also involved the judgment of the Work Group and the ERT.

Grading the Strength of the Recommendations

The strength of a recommendation is graded as level 1 or level 2. Table 43 shows the KDIGO nomenclature for grading the strength of a recommendation and the implications of each level for patients, clinicians, and policy makers. Recommendations can be for or against doing something. Table 44 shows that the strength of a recommendation is determined not only by the quality of the evidence, but also by other, often complex judgments regarding the size of the net medical benefit, values and preferences, and costs. Formal decision analyses including cost analysis were not conducted.

Ungraded Statements

This category was designed to allow the Work Group to issue general advice. Typically an ungraded statement meets the following criteria: it provides guidance that is based on common sense, it provides reminders of the obvious, and it is not sufficiently specific to allow for application of evidence to the issue and therefore it is not based on systematic evidence review. The GRADE system is best suited to evaluate evidence on comparative effectiveness. Some of our most important guideline topics involve diagnosis and staging within CKD, about which the Work Group chose to provide ungraded statements. These statements are indirectly supported by evidence on risk relationships and are the consensus of the Work Group. Thus, we believe that ungraded statements should not be viewed as weaker than graded recommendations. Strong evidence of association is defined as 'significant relative risk of 42 (o0.5)' based on consistent evidence from two or more observational studies, with no plausible confounders.

b Very strong evidence of association is defined as 'significant relative risk of 45 (o0.2)' based on direct evidence with no major threats to validity. c Sparse if there was only one study or if the results include just a few events or observations and were uninformative. Imprecise if the confidence interval spans a range greater than 1 or confidence limits are o0.5 to 42.0 Adapted by permission from Macmillan Publishers Ltd: Kidney International. Uhlig K, Macleod A, Craig J et al. 725 The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.

C Low

The true effect may be substantially different from the estimate of the effect.

D Very low

The estimate of effect is very uncertain, and often will be far from the truth.

Table 42 | Balance of benefits and harm

When there was evidence to determine the balance of medical benefits and harm of an intervention to a patient, conclusions were categorized as follows:

K For statistically significant benefit/harm, report as 'benefit [or harm] of drug X'. K For non-statistically significant benefit/harm, report as 'possible benefit [or harm] of drug X'. K In instances where studies are inconsistent, report as 'possible benefit [or harm] of drug X'. K 'No difference' can only be reported if a study is not imprecise. K 'Insufficient evidence' is reported if imprecision is a factor. Dr Levin is the Executive Director of the BC Renal Agency, which oversees the care, planning, and budgets for kidney services in the province of British Columbia. In this capacity, she has leveraged her epidemiological training, clinical knowledge, and health outcomes research to develop an evidence-based transparent system which enhances the care of patients across the continuum of care (from identification of CKD to dialysis, transplant, and death).

She is active in international activities across the spectrum of kidney activities including her appointment as Secretary General of the International Society of Nephrology (ISN), founding executive committee member of KDIGO, and as co-Chair of the Declaration of Istanbul Custodian group (DICG). Dr Levin has a long-standing clinical and research interest in CKD and CVD, and is Founding Director of the Kidney Function Clinic at St Paul's Hospital.

As an active researcher and mentor, she is involved in a national curriculum development for clinician scientists interested in kidney disease (KRESCENT), and mentors students, residents, and nephrology fellows in Vancouver as well. She has over 210 peer-reviewed publications, numerous book chapters, and is co-editor of a textbook Chronic Kidney Disease: A Practical Guide to Understanding and Management. Her major research areas of interest include non-traditional risk factors for CVD in CKD patients, with particular focus on anemia, phosphate and vitamin D, and progression of CKD variability. His main interests include the epidemiology of CKD and AKI, prospective evaluation of a new method of assessing adequacy in peritoneal dialysis, evaluation of anemia in unreferred patients with CKD and in patients with diabetes, collaborative research with the elderly CKD care team, and the development of information technology-based solutions in the referral and follow-up of patients with kidney disease. Over the last several years, his program has also developed a clinical decision support system to aid management of CKD in primary care and this system is currently running live in a population of over 300,000 primary care patients. Dr Stevens has authored over 90 publications in peerreviewed journals and textbooks, and has given over 100 presentations and 65 guest lectures in national and international society meetings. Advisor/Consultant: Merck Grant/Research Support: Amgen; National Institutes of Health; National Kidney Foundation Speaker: Abbott; Amgen Angel LM de Francisco, MD, PhD, is Head of Dialysis Unit and Nephrology Section, Hospital Universitario Valdecilla, Santander (Spain), and Full Professor of Nephrology at Faculty of Medicine in Cantabria University. He completed his medical residency and nephrology fellowship at Hospital Puerta de Hierro in Madrid, and received his Doctor of Medicine degree from University of Cantabria (Spain). Prof de Francisco is an active member of several professional societies, an Executive member of the KDIGO Board, and was President of the Spanish Society of Nephrology from 2002 to 2008. He has been a frequently invited lecturer, speaking extensively on advancements in treatment of chronic kidney diseases and comorbid conditions such as metabolic bone disease, anemia, dialysis, and kidney transplantation. Prof de Francisco has authored or coauthored over 150 publications, including original peerreviewed articles and book chapters. His primary focus has been on improving outcomes in patients receiving hemodialysis, and on issues surrounding organ transplantation and the impact of treatment guidelines on clinical practice.

Advisor/Consultant

Dr Stevens reported no relevant financial relationships

Advisor/Consultant: Amgen Speaker: Abbott; Fresenius Paul E de Jong, MD, PhD, was Professor of Nephrology and Head, Division of Nephrology of the Groningen University Medical Center in Groningen, the Netherlands from 1992 to 2011. His main research interest is prevention of CKD. From 1980 to 2000, he focused most of his attention on the mechanisms of urinary protein loss in CKD patients and options to lower proteinuria with ACE-I. His studies had indeed shown that such treatment prevented ESRD progression. In 1996, he initiated the PREVEND study which consisted of a large cohort of 8592 subjects followed for the development of kidney disease and CVD. This prospective longitudinal study demonstrated the impact of albuminuria, even in the ranges of microalbuminuria and below, in predicting future cardiovascular and renal events. As former Director of the Groningen Institute of Kidney Diseases, his research program encompasses the studying of underlying susceptibility to kidney damage in health subjects and the identification of common pathophysiological pathways between CKD and CVD. Currently, he serves on the board of KDIGO, CKD-PC, and European Kidney Health Alliance. In 2010, he was the recipient of International Distinguished Medal from the US National Kidney Foundation and was awarded the Officer in the Order of Orange-Nassau for his lifetime achievement by Her Majesty Queen Beatrix of the Netherlands in 2011.

Dr de Jong reported no relevant financial relationships

Kathryn E Griffith, BM, BS, MSc, MRCP, MRCGP, is a general practitioner affiliated with The University Health Centre, York University and York Hospital Foundation Trust. Dr Griffith has a long-standing interest in the relationship between CVD and renal disease from a primary care physician's perspective. In this vein, she has served as a panel member for the Royal College of Physicians (RCP) Edinburgh Consensus Conference on CKD and was involved in the development of the 18-week Commissioning Pathway to CKD with the Department of Health. She is presently a member of the Renal Advisory Group at the Department of Health and a member of both UK Renal Association and British Renal Society. Dr Griffith has also been involved in the education of general practitioners and practice nurses, and most recently she has lectured extensively on various topics such as atrial fibrillation, heart failure, coronary heart areas of research interest include estimation of clearance, anemia protocol development, and translation of evidence into functional guidelines. He is active at the undergraduate medical school level and has coordinated the UBC Renal and Genitourinary Course for 1st year medical students for nearly a decade. He is currently the President of the Western Society of Pediatric Research and an invited member of the Renal Work Group for the World Health Organization's ICD-11 Code Revision.

Dr Uhlig possesses unique knowledge as a methods expert in evidence synthesis and critical literature appraisal in the domain of nephrology.

In 2005, she co-chaired the KDIGO Evidence Rating Group to develop a consensus on grading of KDIGO guidelines and also co-chaired the KDIGO Consensus Conference on Guideline Methodology in October Dr Miskulin reported no relevant financial relationships Amy Earley, BS, is a project coordinator at the Tufts Center for Kidney Disease Guideline Development and Implementation in Boston, MA, USA. She is key in coordinating the guideline development activities within the ERT, especially in the development of the evidence reports for all guidelines. Ms Earley also heads the actual evidence review, which includes running searches, screening, data extraction, drafting of tables and methods sections, proofing of guideline drafts, and critical literature appraisals. She participates in the conduct of research projects at the Center and actively collaborates with other members of the Center on independent research topics and manuscript submissions.

Ms. Earley reported no relevant financial relationships

Shana Haynes, MS, DHSc, is a research assistant at the Tufts Center for Kidney Disease Guideline Development and Implementation in Boston, MA, USA. She participates in all aspects of evidence review and guideline development. She screens abstracts and articles, extracts data, and assists in the drafting and editing of evidence tables. Dr Haynes also assists in the development of clinical practice guidelines and conducts systematic reviews and critical literature appraisals.

Dr Haynes reported no relevant financial relationships

Jenny Lamont, MS, is a project manager and medical writer at the Tufts Center for Kidney Disease Guideline Development and Implementation in Boston, MA, USA. She participates in all aspects of evidence review and guideline development, assists in the preparation of talks and manuscripts, and edits KDIGO draft guidelines currently in progress.

|Table 5.|GFR categories in CKD| |---|---|

|Table 6.|Albuminuria categories in CKD|

|Table 7.|Relationship among categories for albuminuria and proteinuria|

|Table 8.|CGA staging of CKD: examples of nomenclature and comments|

|Table 9.|Prognosis of CKD: Relationship of outcomes and strength of relationship to Cause (C), GFR (G), Albuminuria (A)|

||and other measures|

|Parameter||||Metric units||Conversion factor||SI units|| |---|---|---|---|---|---|---|---|---|---|

|Albumin (serum)||||g/dl||10|||g/l|

|Blood urea nitrogen (BUN)|||mg/dl||0.357|||mmol/l||

|Creatinine (serum)|||mg/dl||88.4|||mmol/l||

|Creatinine clearance|||ml/min||0.01667||ml/s|||

|Hemoglobin||||g/dl||10|||g/l|

|Phosphate (serum)|||mg/dl||0.323|||mmol/l||

|PTH (parathyroid hormone, serum)||pg/ml||0.106|||pmol/l|||

|Urea (plasma)||||mg/dl||0.167|||mmol/l|

|Uric acid||||mg/dl||59.485|||mmol/l|

|Vitamin D, 25-hydroxyvitamin D|||ng/ml||2.496|||nmol/l||

|10.0|86|11.0|97|12.0|108|13.0|119|14.0|130|

|10.1|87|11.1|98|12.1|109|13.1|120|14.1|131|

|10.2|88|11.2|99|12.2|110|13.2|121|14.2|132|

|10.3|89|11.3|100|12.3|111|13.3|122|14.3|133|

|10.4|90|11.4|101|12.4|112|13.4|123|14.4|134|

|10.5|91|11.5|102|12.5|113|13.5|124|14.5|135|

|10.6|92|11.6|103|12.6|114|13.6|125|14.6|136|

|10.7|93|11.7|104|12.7|115|13.7|126|14.7|137|

|10.8|95|11.8|105|12.8|116|13.8|127|14.8|138|

|10.9|96|11.9|107|12.9|117|13.9|128|14.9|139|

|Implications| |---|

|Markers of kidney damage (one or more)|Albuminuria (AERZ30 mg/24 hours; ACRZ30 mg/g [Z3 mg/mmol])| |---|---|

||Urine sediment abnormalities|

||Electrolyte and other abnormalities due to tubular disorders|

||Abnormalities detected by histology|

||Structural abnormalities detected by imaging|

||History of kidney transplantation|

|Decreased GFR|GFRo60 ml/min/1.73 m 2 (GFR categories G3a-G5)|

|Criteria|Comment| |---|---|

|Duration 43 months, based on documentation or||

|inference||

||Structural abnormalities as markers of kidney damage detected by imaging|

||(ultrasound, computed tomography and magnetic resonance with or without contrast,|

||isotope scans, angiography)|

||K Polycystic kidneys|

||K Dysplastic kidneys|

||K Hydronephrosis due to obstruction|

||K Cortical scarring due to infarcts, pyelonephritis or associated with vesicoureteral|

||reflux|

||K Renal masses or enlarged kidneys due to infiltrative diseases|

||K Renal artery stenosis|

||K Small and hyperechoic kidneys (common in more severe CKD due to many|

||parenchymal diseases)|

||K Kidney biopsies in most kidney transplant recipients have histopathologic|

||abnormalities even if GFR is 460 ml/min/1.73 m 2 (GFR categories G1-G2) and|

||ACR is o30 mg/g (o3 mg/mmol)|

||Examples of systemic diseases|Examples of primary kidney diseases (absence of| |---|---|---|

||affecting the kidney|systemic diseases affecting the kidney)|

|Glomerular diseases|Diabetes, systemic autoimmune diseases, systemic|Diffuse, focal or crescentic proliferative GN; focal and|

||infections, drugs, neoplasia (including amyloidosis)|segmental glomerulosclerosis, membranous nephropathy,|

|||minimal change disease|

|Tubulointerstitial|Systemic infections, autoimmune, sarcoidosis,|Urinary-tract infections, stones, obstruction|

|diseases|drugs, urate, environmental toxins||

||(lead, aristolochic acid), neoplasia (myeloma)||

|ACCORD|||

|Age|Upper Limit| |---|---|

|0-6 months|No data|

|7-12 months|No data|

|1-3 years|1500 mg|

|4-8 years|1900 mg|

|9-13 years|2200 mg|

|14-18 years|2300 mg|

|Complication|GFR category (ml/min/1.73 m 2 )|GFR category (ml/min/1.73 m 2 )|GFR category (ml/min/1.73 m 2 )| |---|---|---|---|

||Z90 60-89 45-59 30-44 o30|Z90 60-89 45-59 30-44 o30|Z90 60-89 45-59 30-44 o30|

|Anemia 1|4.0% 4.7% 12.3% 22.7% 51.5%|4.0% 4.7% 12.3% 22.7% 51.5%|4.0% 4.7% 12.3% 22.7% 51.5%|

|Hypertension 2|18.3% 41.0% 71.8% 78.3% 82.1%|18.3% 41.0% 71.8% 78.3% 82.1%|18.3% 41.0% 71.8% 78.3% 82.1%|

|25(OH) Vit D deficiency 3 14.1% 9.1%|10.7%|27.2%|367|

|Acidosis 4|11.2% 8.4% 9.4% 18.1% 31.5%|11.2% 8.4% 9.4% 18.1% 31.5%|11.2% 8.4% 9.4% 18.1% 31.5%|

|Hyperphosphatemia 5|7.2% 7.4% 9.2% 9.3% 23.0%|7.2% 7.4% 9.2% 9.3% 23.0%|7.2% 7.4% 9.2% 9.3% 23.0%|

|Hypoalbuminemia 6|1.0% 1.3% 2.8% 9.0% 7.5%|1.0% 1.3% 2.8% 9.0% 7.5%|1.0% 1.3% 2.8% 9.0% 7.5%|

|Hyperparathyroidism 7|5.5% 9.4% 23.0% 44.0% 72.5%|5.5% 9.4% 23.0% 44.0% 72.5%|5.5% 9.4% 23.0% 44.0% 72.5%|

|Abbreviations: CKD, chronic kidney disease; GFR, glomerular filtration rate.||||

|*Note that modification of prevalence according to albuminuria categories data is||||

|not yet available to inform this table adequately, though there are limited data to||||

|suggest increasing prevalence of hypoalbuminemia, hypertension, anemia, and||||

|acidosis as albuminuria category increases||||

|1 Defined as hemoglobin levels o12 g/dl (120 g/l) for women; o13.5 g/dl (135 g/l)||||

|for men||||

|2 Defined as a systolic blood pressure Z140 mm Hg, diastolic blood pressure||||

|Z90 mm Hg, or self-reported use of antihypertensive medication|Z90 mm Hg, or self-reported use of antihypertensive medication|Z90 mm Hg, or self-reported use of antihypertensive medication||

|Age or gender group|Hemoglobin threshold: g/dl (g/l)| |---|---|

|Children||

|6 mo-5 yr|11.0 (110)|

|5-12 yr|11.5 (115)|

|12-15 yr|12.0 (120)|

|Non-pregnant females 415 yr|12.0 (120)|

|Pregnant females 415 yr|11.0 (110)|

|Men 415 yr|13.0 (130)|

|Abbreviations: mo, month; yr, year.||

|Reproduced with permission from World Health Organization. Worldwide pre-|Reproduced with permission from World Health Organization. Worldwide pre-|

|valence of anaemia 1993-2005: WHO global database on anaemia. 368 In: de Benoist|valence of anaemia 1993-2005: WHO global database on anaemia. 368 In: de Benoist|

|B, McLean E, Egli I and Cogswell M (eds), 2008; accessed: http://whqlibdoc.who.int/|B, McLean E, Egli I and Cogswell M (eds), 2008; accessed: http://whqlibdoc.who.int/|

|publications/2008/9789241596657_eng.pdf.||

|3.3.3: In people with GFR o45 ml/min/1.73m 2 (GFR| |---|

|categories G3b-G5), we suggest maintaining serum|

|phosphate concentrations in the normal range|

|according to local laboratory reference values. (2C)|

|3.3.4: In people with GFR o45 ml/min/1.73m 2 (GFR|

|categories G3b-G5) the optimal PTH level is not|

|known. We suggest that people with levels of intact|

|PTH above the upper normal limit of the assay|

|are first evaluated for hyperphosphatemia, hypo-|

|calcemia, and vitamin D deficiency. (2C)|

|RATIONALE|

|Higher serum phosphate concentrations are associated with|

|mortality and experimental data suggests that serum|

|phosphate concentration is directly related to bone disease,|

|vascular calcification and CVD. Serum phosphate, calcium,|

|and PTH concentrations are all inter-related in patients with|

|CKD. Randomized studies linking manipulation of these|

|parameters to clinical outcomes are lacking but systematic|

|review indicates that earlier phosphate control may help|

|reduce the early clinical consequences of CKD-MBD. Simi-|

|larly there is insufficient evidence that any specific phosphate|

|binder significantly impacts patient-level outcomes.|

|Treatment of CKD-MBD|

|||Ranked|| |---|---|---|---|

|Aluminium hydroxide|1.425-2.85 g|Extensive clinical experience in CKD and ESRD, no RCT comparison versus placebo.|1|

|||Aluminium accumulates in bone and neural tissue with long-term use, avoids||

|||calcium||

|Calcium citrate|1.5-3 g|Limited trial evidence in ESRD. Reduction in phosphate and elevation in calcium|2|

|||dose-dependent||

||carbonate 0.33-0.66 g)|||

|Magnesium carbonate|plus|||

|combination|Magnesium carbonate|||

||235 mg, 3-10 tablets daily|||

|Calcium carbonate|3-6 g|Extensive clinical experience in CKD and ESRD, limited RCT evidence versus placebo.|4|

|||Reduction in phosphate and elevation in calcium both dose-dependent||

|Calcium acetate|3-6 g|Extensive clinical experience in ESRD; RCT evidence comparing to other binders.|4|

|||Reduction in phosphate and elevation in calcium dose-dependent but less than with||

|||calcium carbonate||

|Lanthanum carbonate|3 g|Extensive prospective cohort evidence, RCT evidence compared to other phosphate|5|

|||binders. Potential for accumulation in bone and other tissues, avoids calcium||

|Sevelamer-HCl|4.8-9.6 g|Extensive prospective cohort evidence in ESRD; RCT evidence compared to other|6|

|||phosphate binders; surrogate and patient-centered outcomes, avoids calcium||

|Sevelamer carbonate|4.8-9.6 g|RCT evidence compared to other phosphate binders; equivalency studies compared|6|

|||to sevelamer-HCl, avoids calcium||

|||Dose, frequency and route of|Special considerations for CKD and clinical trial| |---|---|---|---|

||Corticosteroid use|70 mg weekly, oral|No reported adverse events specific to CKD|

||Corticosteroid use|5-10 mg/kg daily for up to 6 months|Moderate or severe renal impairment: avoid|

||Paget's disease||No data in CKD|

||Postmenopausal osteoporosis|3 mg every 3-months intravenous|No reported adverse events specific to CKD|

||Paget's disease|30 mg weekly for 6 weeks, intravenous|AKI reported|

||Corticosteroid use|35 mg weekly, oral|No reported adverse events specific to CKD|

||Paget's disease|||

||||No data in CKD|

||Paget's disease||graded dose reduction|

||||No data in CKD, AKI reported in non-CKD|

|Evidence Base| |---|

|Modification of risk factors|

|includes:|

|1. Smoking cessation|

|2. Exercise|

|3. Weight reduction to optimal targets|

|4. Lipid modification recognizing that the risk reduction|

|associated with statin therapy in adults with CKD is|

|Study|Population|PAD definition|Outcome of interest| |---|---|---|---|

||||normal kidney function|

||with known CHD|revascularization, or lumbar|and 2.73% per year with CrCl 60, 30-59, and|

|||sympathectomy)|30 ml/min/1.73 m 2 , respectively|

||age 65+|(bypass surgery, angioplasty, or|highest quintile of cystatin C (Z1.28 mg/l) versus|

|||amputation)|lowest (r0.9 mg/l)|

|De Vinuesa et al. 582 102 adults in a CKD clinic, mean age 70 ± 11 years, GFR 15-60 ml/min/ 1.73 m 2|ABI o0.9|17% signs and symptoms of PAD, which had passed unnoticed; 32% had ABI o0.9 (mean 0.64 ± 0.25)||

||index recording and GFR measured||28% CKD alone, 26% PAD alone, and 18% for|

||within 90 d)||neither condition|

||Multi-Ethnic Study of Atherosclerosis||with diabetes (odds ratio 1.90, 95% CI 1.19-3.04)|

||||but not in those without|

|Lash et al. 583|3612 subjects age 58.2±11.0 years in the Chronic Renal Insufficiency|ABI o0.9|Overall, 16% prevalence of PAD in subjects with GFRo60 ml/min/1.73 m 2 , increasing from 4% in|

||Cohort study||those with GFR460 to 22% in those with|

||||GFRo30 ml/min/1.73 m 2|

||proteinuria assessment, median|PAD|for PVD, adjusted rates increased with lower GFR|

||follow-up 35 months (IQR 22-44)|||

|100|||Kidney International Supplements (2013) 3, 91-111|

|c h a p t e r 4| |---|

|Radiocontrast|

|4.5.2: We recommend that all people with GFR o60 ml/ min/1.73m 2 (GFR categories G3a-G5) undergoing|

|elective investigation involving the intravascular|

|administration of iodinated radiocontrast media|

|should be managed according to the KDIGO|

|Clinical Practice Guideline for AKI including:|

|K Avoidance of high osmolar agents (1B);|

|K Use of lowest possible radiocontrast dose (Not|

|Graded);|

|K Withdrawal of potentially nephrotoxic agents|

|before and after the procedure (1C);|

|K Adequate hydration with saline before, during,|

|and after the procedure (1A);|

|K Measurement of GFR 48-96 hours after the|

|procedure (1C).|

|Advanced age| |---|

|High burden of coexisting illnesses such as diabetes|

|Hypoalbuminemia|

||c h a p t e r 4| |---|---|

|4.6.8: CKD disease management programs should be||

|developed in order to optimize the community||

|management of people with CKD and reduce the||

|risk of hospital admission. (Not Graded)||

|4.6.9: Interventions to reduce hospitalization and mor-||

|tality for people with CKD should pay close atten-||

|tion to the management of associated comorbid||

|conditions and cardiovascular disease in particular.||

|(Not Graded)||

|Kidney International Supplements (2013) 3, 91-111|109|

|Disease monitoring| |---|

|Integration with other chronic disease management programs including|

|diabetes, hypertension and heart failure|

|Medication management and dietary advice|

|Anemia management programs|

|Vaccination programs|

|Information and psychosocial support|

|Renal replacement therapy (dialysis and transplant) education|

|Advanced care planning and end-of-life care (where appropriate)|

||||||Persistent albuminuria categories||| |---|---|---|---|---|---|---|---|

||||||Description and range|||

||||||A1|A2|A3|

||||||Normal to mildly increased|Moderately increased|Severely increased|

||||||< 30 mg/g|30-300 mg/g|> 300 mg/g|

||||||< 3 mg/mmol|3-30 mg/mmol|> 30 mg/mmol|

|||G1|Normal or high|≥90||Monitor|Refer*|

|Consequences of late referral| |---|

|Variable|Early referral mean (SD)|Late referral mean (SD)|P value| |---|---|---|---|

|Overall mortality, %|11 (3)|23 (4)|o0.0001|

|1-year mortality, %|13 (4)|29 (5)|0.028|

|Hospital length of stay, days|13.5 (2.2)|25.3 (3.8)|0.0007|

|Serum albumin at RRT start, g/dl [g/l]|3.62 (0.05) [36.2 (0.5)]|3.40 (0.03) [34.0 (0.3)]|0.001|

|Hematocrit at RRT start, %|30.54 (0.18)|29.71 (0.10)|0.013|

|Abbreviation: RRT, renal replacement therapy.||||

|Adapted from Am J||||

|No. of reports|or articles|yielded||15|||||||2||||||1|||||2|||||1 SR + 1 RCT|||1|1|3 SR+ 1 RCT|||||||||||| |---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

||Methodological|approach||SR|Equation must be|validated in an external|dataset||||Studies identified by|WG|||||Search for SRs|||||Search for recent|guidelines, SRs, RCTs,|observational studies, or|narrative reviews||Review of Cochrane SRs|plus systematic search|for RCTs published after|search dates in most|recent Cochrane SR|SR|Review of studies|identified by WG|Review of Cochrane SRs|plus systematic search|for RCTs published after|search dates in most|recent Cochrane SR|||||

||Inclusion|criteria||Overall N|4100 N|450 for|subgroups||||Equation|must be|validated in|an external|dataset|N 4100|None|||||None|||||N 4100|||N 4100|N 4100|N 4100||||||||||||

|||Study design||Cross-sectional or|diagnostic test|study|||||Longtudinal cohort|study|||||SR of case-control|and cohort studies||||Narrative review of|case-control|studies;|observational|cohort studies|RCT|||RCT|RCT|RCT||||||||||||

||Outcome (ranked|by importance)||Bias precision,|accuracy expressed|as P 30 w|||||ESRD,|mortality|||||Nephrogenic|fibrosing|dermopathy|||Categorical kidney|outcomes||||ESRD, categorical or|continuous kidney|function; QOL and|BP control as|adverse events|Mortality,|cardiovascular|events, ESRD, CKD|progression, gout|attacks; QOL and BP|control as adverse|events; proteinuria|Mortality, ESRD|ESRD, mortality,|categorical or|continuous kidney|function|

|Treatment, Comparator or|predictor or alternative test|index test or gold standard||GFR prediction based Gold standard measure|on SCr or SCysC must of GFR (e.g.,|be directly traceable to iothalamate, EDTA,|(not just indirectly iohexal, inulin clearance)|calibrated to) IDMS Not 24-hr urine|standards collection||Candidate predictors NA|had to include at least|age, sex, SCr, and DM|status|||Gadolinium exposure No gadolinium|exposure||||Exposure to phosphate-No exposure to|containing bowel phosphate-containing|preparation bowel preparation|||Bicarbonate or citrate No bicarbonate or|citrate||Allopurinol No allopurinol|Early start of dialysis Late start of dialysis|Reduced protein intake Usual protein intake||||||||||||

|||Population||Patients in steady state|with or without CKD|and other special|populations (DM, HTN,|KTR or donors, various|age groups, races, or|ethnic groups)|GFR o60 ml/min/ 1.73 m 2 and/or|kidney transplant||||GFR o60 ml/min/ 1.73 m 2 and/or|kidney transplant|||Any GFR category;|individuals without|CKD|||GFR o60 ml/min/ 1.73 m 2 and/or kidney|transplant|GFR o60 ml/min/ 1.73 m 2 and/or kidney|transplant with or|without hyperuricemia|GFR o30 ml/min/ 1.73 m 2|GFR o60 ml/min/ 1.73 m 2 and/or|kidney transplant||||||||||||

|||Question||How do SCr-or|SCysC-based prediction|equations perform|compared to gold|standard measurement|of GFR?||What prediction|equations exist to|predict kidney failure?||||What is the incidence|of NFD after exposure|to gadolinium?|||What is the incidence|of AKI after taking a|phosphate-containing|bowel preparation?||Does treatment with|bicarbonate in CKD|improve clinical|outcomes?|Does treatment with|allopurinol in CKD|improve clinical|outcomes?|When should dialysis be|started: early or late?|Should patients with|CKD be on a protein-|restricted diet?|||||

|||Topic|Non-Treatment|Prediction|equations for|GFR|||||Prediction|equations for risk of|kidney failure||||Gadolinium|exposure and|nephrogenic|fibrosing|dermopathy|AKI and phosphate-|containing bowel|preparations||Treatment|Treatment with|bicarbonate||Treatment with|allopurinol|Timing of initiation|of RRT in CKD|Protein restriction|Abbreviations:|||||||||

||||||Articles|| |---|---|---|---|---|---|---|

||Systematic||||with full|Articles|

||review|||Articles|text|used in|

|Non-treatment topics|||||||

|Prediction equations for eGFR|Y|MEDLINE search from 2006 until|''kidney,'' and ''prediction,''|2921|86|15|

|||2011, with an update in June 2011|''equation,'' ''formula,'' or||||

||||''regression analysis''||||

|Prediction equations for risk of|N|nd|nd|10*|10|2|

|kidney failure or death|||||||

|Risk from gadolinium for|Y|MEDLINE search from 1996 until|''kidney,'' and ''gadolinium,''|1 w|0|0|

|nephrogenic fibrosing||2011 was run in March 2011|''nephrogenic fibrosing||||

|dermopathy|||dermopathy,'' or ''nephrogenic||||

||||systemic fibrosis,'' and systematic||||

||||review||||

|Risk for nephropathy from|N|MEDLINE search for recent (2008-|''Phosphate nephropathy''|2|2|2|

|phosphate-containing bowel||2011) narrative reviews was run in|||||

|preparations||March 2011|||||

|Treatment topics|||||||

|Treatment with bicarbonate|Y|MEDLINE search from 2005 until|''randomized controlled trial,'' and|3981|6|1|

|||2011, with an update in May 2011|''kidney,'' or ''metabolic acidosis,''||||

||||and ''bicarbonate''||||

|Treatment with allopurinol|Y|MEDLINE search from 1996 until|''randomized controlled trial,'' and|393|4|1|

|||2011, with an update in May 2011|''kidney,'' and ''allopurinol''||||

|Earlier versus later initiation of|N|n d|n d|8 z|8|1|

|RRT in CKD|||||||

|Treatment with protein|Y|Three Cochrane systematic reviews|''randomized controlled trial,'' and|561|1|1|

|restriction||were identified and used instead of|''kidney,'' and ''diet, protein-||||

|||a de novo systematic review.|restricted''||||

|||MEDLINE search from 1996-2011,|||||

|||with an update in March 2011|||||

|Step 1: Starting grade for|||| |---|---|---|---|

|quality of evidence based||||

|Randomized trials = High|Study quality|Strength of association||

||-1 level if serious limitations|+1 level is strong a , no plausible||

||-2 levels if very serious limitations|confounders||

|||+2 levels if very strong b , no major||

||Consistency|threats to validity||

||-1 level if important inconsistency|Other||

|||+1 level if evidence of a||

||Directness|dose-response gradient||

||-1 level if some uncertainty|+1 level if all residual plausible||

||-2 levels if major uncertainty|confounders would have||

|||reduced the observed effect||

||Other:|||

||-1 level if sparse or imprecise data c|||

||-1 level if high probability of|||

||reporting bias|||

||Quality of|| |---|---|---|

|Grade|evidence|Meaning|

|A|High|We are confident that the true effect lies close to that of|

|||the estimate of the effect.|

|B|Moderate||

Ms. Lamont reported no relevant financial relationships

Acknowledgments

TABLES KDIGO nomenclature and description for grading recommendations

Criteria for definition of CKD

Classification of CKD based on presence or absence of systemic disease and location within the kidney of pathologic-anatomic findings

Annual percentage change in GFR across diagnosis categories

Sources of error in GFR estimating using creatinine

Equations based on serum creatinine assays in adults that are traceable to the standard reference material

Performance comparison of creatinine-based GFR estimating equations in North America, Europe, and Australia

Performance comparison of creatinine-based GFR estimating equations outside of North America, Europe, and Australia

Sources of error in GFR estimating using cystatin C

Equations based on IDMS traceable creatinine and IFCC traceable cystatin C assays

Performance comparison of cystatin C-based estimating equations in North American and European populations

Strengths and limitations of GFR measurement methods and markers

Factors affecting urinary ACR

Decline in kidney function in various populations (longitudinal studies only)

Decline in kidney function in CKD populations

Studies evaluating rapid progression (general population studies only)

CKD progression and risk of all-cause mortality and ESRD using baseline (first) eGFR

Association between absolute and percentage change in kidney function and risk of ESRD, based on adjustment for eGFR at the first and last measurement

Intensive versus normal glycemic control and albuminuria outcome

Recommended Daily Intake of sodium for healthy children

Prevalence of CKD complications by GFR category derived from CKD cohorts

Hemoglobin cutoffs for people living at sea level

Phosphate binding agents in routine clinical practice and their ranked cost

Summary data for bisphosphonates and CKD

Peripheral arterial disease and CKD

Cautionary notes for prescribing in people with CKD

Risk factors for infection in people with CKD

Components of community CKD management programs

Early versus late referral: consequences and benefits

Outcomes of early versus late referral

Topics of interest for the management of CKD guideline

Literature yield of primary articles for all topics

Classification of study quality

GRADE system for grading quality of evidence

Final grade for overall quality of evidence

Balance of benefits and harm

KDIGO nomenclature and description for grading recommendations

Determinants of strength of recommendation

HbA 1c (%)À2.15]Â10.929Abbreviations: DCCT, Diabetes Control and Complications Trial; IFCC, International Federation of Clinical Chemistry and Laboratory Medicine.Source: Diabetes UK, www.diabetes.org.uk.ForewordKidney International Supplements (2013) 3, 2; doi:10.1038/kisup.2012.74

Criteria for CKD (either of the following present for 43 months)

19 iteria for definition of CKD19

Continued Kidney transplant recipients have an increased risk for mortality and kidney failure compared to populations without kidney disease K Kidney transplant recipients routinely receive subspecialty care Abbreviations: ACR, albumin-to-creatinine ratio; AER, albumin excretion rate; CKD, chronic kidney disease; eGFR, estimated glomerular filtration rate; GBM, glomerular basement membrane; GFR, glomerular filtration rate; RBC, red blood cell; SCr, serum creatinine; WBC, white blood cell.

Classification* of CKD based on presence or absence of systemic disease and location within the kidney of pathologicanatomic findings : ANCA, antineutrophil cytoplasmic antibody; CKD, chronic kidney disease, GN, glomerulonephritis Genetic diseases are not considered separately because some diseases in each category are now recognized as having genetic determinants. *Note that there are many different ways in which to classify CKD. This method of separating systemic diseases and primary kidney diseases is only one, proposed by the Work Group, to aid in the conceptual approach.

GFR categories in CKD

Albuminuria categories in CKD

Relationship among categories for albuminuria and proteinuria

CGA staging of CKD: examples of nomenclature and comments Patients above the thick horizontal line are likely to be encountered in nephrology practice. Patients below the thick horizontal line are likely to be encountered in primary care practice and in nephrology practice.

Note that the + designations refer to strength of relationship not strength of evidence to support, and are based on consensus overview by the Work Group members. Adapted with permission from Uhlig K, Levey AS.

Prognosis of CKD by GFR and albuminuria category. Green, low risk (if no other markers of kidney disease, no CKD); Yellow, moderately increased risk; Orange, high risk; Red, very high risk. CKD, chronic kidney disease; GFR, glomerular filtration rate; KDIGO, Kidney Disease: Improving Global Outcomes. Modified with permission from Macmillan Publishers Ltd: Kidney International. Levey AS, de Jong PE, Coresh J, et al.

J Am Soc Nephrol 20: 2305-2313, 2009; permission conveyed through Copyright Clearance Center, Inc.; accessed http://jasn.asnjournals.org/content/20/11/2305.full.pdf

|Vascular diseases|Atherosclerosis, hypertension, ischemia, cholesterol|ANCA-associated renal limited vasculitis, fibromuscular|

||emboli, systemic vasculitis, thrombotic|dysplasia|

||microangiopathy, systemic sclerosis||

|Cystic and congenital|Polycystic kidney disease, Alport syndrome,|Renal dysplasia, medullary cystic disease, podocytopathies|

|diseases|Fabry disease||

|GFR category GFR (ml/min/1.73 m 2 ) Terms||| |---|---|---|

|G1|Z90|Normal or high|

|G2|60-89|Mildly decreased*|

|G3a|45-59|Mildly to moderately decreased|

|G3b|30-44|Moderately to severely decreased|

|G4|15-29|Severely decreased|

|G5|o15|Kidney failure|

|||ACR (approximate|ACR (approximate|ACR (approximate| |---|---|---|---|---|

|Category|equivalent) (mg/24 hours) (mg/mmol) (mg/g) AER|Terms|||

|A1|o30|o3|o30|Normal to mildly|

|||||increased|

|A2|30-300|3-30|30-300 Moderately increased*||

|A3|4300|430|4300|Severely increased**|

|Categories| |---|

|Normal to mildly increased|Moderately increased|Severely increased| |---|---|---|

|< 30 mg/g|30-300 mg/g|> 300 mg/g|

|< 3 mg/mmol|3-30 mg/mmol|> 30mg/mmol|

||GFR|Albuminuria||| |---|---|---|---|---|

|recipient|||||

|||||gene|

|acidosis|||||

|disease||||hypertension, likely to include patients with genetic|

|||||predisposition-more common in blacks-who should|

|||||be referred to nephrologist because of severely|

|||||decreased GFR|

|diabetes and hypertension||||decreased GFR|

|diabetes and hypertension||||albuminuria|

|diabetes and hypertension|||||

|Abbreviations: CGA, Cause, GFR category and albuminuria category; CKD, chronic kidney disease; GFR, glomerular filtration rate.|||||

|Note:|||||

|(C), GFR (G), Albuminuria (A) and| |---|

|||Normal to mildly increased|Moderately increased|Severely increased| |---|---|---|---|---|

|||< 30 mg/g|30-300 mg/g|> 300 mg/g|

|||< 3 mg/mmol|3-30 mg/mmol|> 30 mg/mmol|

||Normal or high|≥90|||

|G2|Mildly decreased|60-89|||

|G3a|Mildly to moderately decreased|45-59|||

|G3b|Moderately to severely decreased|30-44|||

|G4|Severely decreased|15-29|||

|G5|Kidney failure|< 15|||

|Figure 9 ||||||

|Annualized percentage change|| |---|---|

|Disease|[number of patients]|

|Focal and segmental|-13.3% [N=34]|

|glomerulosclerosis||

|Hemolytic uremic syndrome|-1.3% [N=27]|

|Other glomerular|-15.5% [N=51]|

|Obstructive uropathy|-4.6% [N=109]|

|Aplastic/hypoplastic/dysplastic|-3.3% [N=96]|

|kidneys||

|Reflux nephropathy|-3.8% [N=82]|

|Autosomal recessive polycystic|-4.4% [N=18]|

|kidney disease||

|Other non-glomerular|-2.5% [N=119]|

|Abbreviation: GFR, glomerular filtration rate.||

|Data from Furth et al. 72||

|Source of error| |---|

||SCr assay method||Samples from MDRD Study were assayed|from 1988 to 1994 with the Beckman|Synchron CX3 kinetic Jaffe assay (Global|Medical Instrumentation, Inc., Ramsey,|Minnesota). Samples were reassayed in|2004 with the same instrument. The|Beckman assay (Global Medical|Instrumentation, Inc., Ramsey, Minnesota)|was calibrated to the Roche enzymatic|assay (Roche Diagnostics, Basel,|Switzerland), which is traceable to an IDMS|assay at NIST.|SCr values were recalibrated to|standardized SCr measurements at the|Cleveland Clinic by using a Roche enzymatic|assay (Roche-Hitachi P-Module instrument|with Roche Creatininase Plus assay,|Hoffman-La Roche, Basel, Switzerland).|||SCr levels were measured by using a Hitachi|enzymatic creatinine assay and the values|obtained were compared with those of the|Cleveland Clinic.|SCr levels were assayed by both enzymatic|and noncompensated kinetic Jaffe methods|for the 116 patients in the inulin clinical|study and by an enzymatic method for the|132 inpatients at Tokyo Women's Medical|University between 2003 and 2004 and the|168 patients with CKD at the University of|Tsukuba Hospital from 1988 to 1994. The|SCr levels of the samples from the 101|patients from Tokyo Women's Medical|University between 2001 and 2002 were|measured by a noncompensated kinetic|Jaffe method. SCr levels used in the inulin|clinical trial were simultaneously measured|by both the noncompensated kinetic Jaffe|method and enzymatic method at the|International Organization for|Standardization-approved central|laboratory. SCr values from the|noncompensated Jaffe method were 0.207|higher than those from the enzymatic|method throughout the measured range,|based on calibrated standards which were|indirectly calibrated with IDMS.| |---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

||GFR measurement method||125 I-Iothalamate (urine); GFR|measured in ml/min per 1.73 m 2 ;|mean GFR, 39.8 ml/min per 1.73 m 2|(SD, 21.2)||||||||||125 I-Iothalamate (urine); GFR|measured in ml/min per 1.73 m 2 ;|mean GFR, 68 ml/min per 1.73 m 2|(SD, 40)|||||Inulin (urine) GFR measured in ml/|min per 1.73 m 2 (ND for|development or internal validation|set)|Inulin (urine) GFR measured in ml/|min per 1.73 m 2 (ND for|development or internal validation|set)||||||||||||||||||||

|Development and internal|validation population, N||1628 patients enrolled in the|MDRD Study (mean age, 50.6 y)||||||||||||8254 participants from 6 research|studies and 4 clinical populations|(mean age, 47 y)||||||413 Japanese patients in 80|medical centers (mean age, 51.4 y)|||248 inpatients with CKD for|estimating and determining the|coefficient of the MDRD Study|equation for Japanese patients|(mean age, 50.1 y)|||||||||||||||||||

||Equation||175 Â SCr À1.154 Â age À0.203 Â 0.742 (if female)|Â 1.212 (if black)|||175 Â SCr À1.154 Â age À0.203 Â 0.742 (if female)||||||||141 Â min(SCr/k, 1) a Â max(SCr/k,|1) À1.209 Â 0.993 age Â 1.018|(if female) Â 1.159 (if black),|where k is 0.7 for females and 0.9 for|males, a is À0.329 for females and À0.411|for males, min indicates the minimum of|SCr/k or 1, and max indicates the|maximum of SCr/k or 1.|Â age À0.203 0.808 Â 175 Â SCr À1.154|Â 0.742 (if female)|||Â age À0.203 0.741 Â 175 Â SCr À1.154|Â 0.742 (if female)|||||||||||||||||||||||

||Study Equation name|North America, Europe, and Australia|Levey et al. 86 MDRD equation||||MDRD equation without ethnicity|factor*||||||Levey et al. 87 CKD-EPI equation|||||||Outside of North America, Europe, and Australia|Horio et al. 88 MDRD equation with Japanese|coefficient|||Imai et al. 89 Japanese-modified MDRD|equation||||||||||||||||||||||||

||SCr assay method|Fasting SCr levels measured by using a|Roche enzymatic assay (Roche Diagnostics,|Indianapolis, IN) and values adjusted by|using IDMS reference SCr (SRM 967) from|NIST. SCr levels also measured by a Roche|kinetic Jaffe assay Roche (Roche|Diagnostics, Indianapolis, IN) without|adjustments to IDMS reference. SCr levels|obtained from enzymatic and Jaffe assays|were used in each estimated GFR equation|accordingly.|SCr levels measured by Hitachi enzymatic|assay and values obtained compared with|those of the Cleveland Clinic.||SCr levels measured by Hitachi enzymatic|assay (Hitachi, Tokyo, Japan) and values|obtained compared with those of the|Cleveland Clinic.|||Serum and urine creatinine levels measured|by using kinetic Jaffe assay.|||SCr levels measured by using Hitachi kinetic|Jaffe assay and values calibrated to the|Cleveland Clinic Laboratory.||||Fasting SCr levels measured by using a|Roche enzymatic assay (Roche Diagnostics,|Indianapolis, IN) and values adjusted by|using IDMS reference SCr (SRM 967) from|NIST. SCr also measured by a Roche kinetic|Jaffe assay (Roche Diagnostics, Indianapolis,|IN) without adjustments to IDMS reference.|SCr levels obtained from enzymatic and|Jaffe assays used in each estimated GFR|equation accordingly.| |---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

|Development and internal|Equation validation population, N GFR measurement method|175 Â SCr À1.154 Â age À0.203 Â 0.742 250 cases of Thai patients with CKD 99m Tc-DTPA (plasma); GFR|(if female) Â 1.129 (if Thai) patients who were in stable measured in ml/min per 1.73 m 2|condition (mean age, 59.5 y) (ND for development or internal|validation set)||||||||0.813 Â 141 Â min(SCr/k, 1) Inulin (urine) GFR measured in|ml/min per 1.73 m 2 (ND for|development or internal validation|set)|171 Â SCr À1.004 Â age À0.287 413 Japanese patients in 80 Inulin (urine)|Â 0.782 (if female) medical centers; data collected Mean GFR, 59.1 ml/min per|from 1 December 2006 to 20 April 1.73 m 2 (SD, 35.4)|2007 (mean age, 51.4 y)|194 Â SCr À1.094 Â age À0.287|Â 0.739 (if female)|186 Â SCr À1.154 Â age À0.203 1628 patients whose GFR was 125 I-Iothalamate (urine)|Â 0.742 (if female) measured as part of the MDRD GFR measured in ml/min per|Study (mean age, 50.6 y) 1.73 m 2 ; mean GFR, 39.8 ml/min|per 1.73 m 2 (SD, 21.2)|186 Â SCr À1.154 Â age À0.203 Â 0.742 (if 454 patients from 9 renal institutes 99m Tc-DTPA (plasma) GFR|female) Â 1.227 (if Chinese), with SCr calibrated of university hospitals located in 9 measured in ml/min per 1.73 m 2|to the Cleveland Clinic geographic regions of China (mean (ND for development or internal|age, 49.9 y) validation set)|206 Â SCr À1.234 Â age À0.227 Â 0.803 (if female),|with SCr calibrated to the Cleveland Clinic|375.5 Â SCr À0.848 Â age À0.364 Â 0.712 (if female); 250 Thai patients with CKD who 99m Tc-DTPA (plasma) GFR|r 2 = 0.869 were in stable condition (mean measured in ml/min per 1.73 m 2|age, 59.5 y) (ND for development or internal|validation set)|||||||

||Equation name|MDRD equation with Thai|coefficient||||||||||CKD-EPI equation with Japanese|coefficient|||JSN-CKDI equation (equation 2)||||3-variable Japanese equation|(equation 4)|Original MDRD equation, calibrated|to the Cleveland Clinic creatinine|measurements (study equation 2) w||Original MDRD equation, calibrated|to Cleveland Clinic creatinine|measurements, with Chinese|coefficient (study equation 4) w|Chinese equation (study|equation 6) z|Thai estimated GFR equation||||||||||

||Study|Praditpornsilpa et al. 90|||||||||||Horio et al. 88||||Matsuo et al. 91||||||Levey et al. 92||||Ma et al. 93||||||Praditpornsilpa et al. 90||||||||||

|Results| |---|

|GFR estimation|

|Measured GFR|

|1.4.3.6: If cystatin C is measured, we suggest that health| |---|

|professionals (2C):|

|Kidney International Supplements (2013) 3, 19-62| |---|

|Results|Bias ml/min/ Precisionw Accuracyz|1.73 m 2 *||-6.3 (-7.8, -5.4) 19.4 (17.4, 83%|21.1)|||-6.0 (-7.1, -4.9) 18.7 (17.5, 84%|20.0)|-4.9 (-5.9, -4.2) 15.3 (14.0, 92%|16.3)|-3.7 (-4.6, -2.8) 15.4 (14.3, 87%|16.5)||-3.4 (-4.4, -2.3) 16.4 (14.8, 86%|17.8)|-3.9 (-4.5, -3.2) 13.4 (12.3, 92%|14.5)|-3.5 (-4.1, -2.8) 13.9 (12.9, 92%|14.7)||-2 (-3, -1) 0.229 84%|(0.210, (83, 85)|0.247)|3 (2, 3) 0.264 73%|(0.239, (72, 74)|0.289)|2 (1, 2) 0.248 79%|(0.223, (78, 80)|0.271)|0 (0, 1) 0.193 90%|(0.174, (89, 91)|0.211)| |---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

||Equations|||Re-expressed MDRD||||CKD-EPI cystatin C 2011||CKD-EPI creatinine-cystatin C|2011|CKD-EPI creatinine 2009|||CKD-EPI cystatin C 2012||CKD-EPI creatinine-cystatin C|2012|Average of CKD-EPI creatinine|2009 and CKD-EPI cystatin C|2012|Re-expressed MDRD|||CKD-EPI cystatin C (alone) 2011|||CKD-EPI cystatin C 2011|CKD-EPI creatinine-cystatin C|2011||||

|GFR estimate|mGFR (SD) Serum creatinine (SCr) Cystatin C|calibration and assay calibration and|detail assay detail|70 (41) Y (IFCC SRM 967) Y (IRMM)||||||||||||||||||34 (17) Y (IFCC SRM 967) Y (IRMM)||||||||||||

|mGFR|Reference|standard||Exogenous|filtration|markers other|and urinary|iothalamate (U)||||||||||||||51 Cr-EDTA||||||||||||

||N|||1119||||||||||||||||||438||||||||||||

|Study description|Population (subgroup)|||RS/CP: 5 studies (2 RS and 3 CP)|using equations developed in CKD|population [3% black, Mean age 50y,|53% DM]|||||RS/CP: 5 studies (2 RS and 3 CP)|using equations developed in|diverse dataset [3% black, Mean age|50y, 53% DM]|||||||CP: Clinical population in Paris,|France [29% women, 79% white, 8%|black, 13% other, Mean age 59y,|22% DM, 16%]|||||||||

||Author|||Inker LA et al. 113|Multi|||||||||||||||||Stevens, LA et al. 117|France|||||||||||

|Approach|Strengths|Limitations| |---|---|---|

|Methods|||

|Urinary clearance|||

|Bladder catheter and continuous|K Gold standard method|K Invasive|

|intravenous infusion of marker|||

|Spontaneous bladder emptying|K Patient comfort|K Possibility of incomplete bladder emptying|

||K Less invasive|K Low flow rates in people with low levels of GFR|

|Bolus administration of marker|K Shorter duration|K Rapidly declining plasma levels at high levels of GFR|

|||K Longer equilibration time in extracellular volume expansion|

|24 h urinary collection||K Cumbersome|

|||K Prone to error|

|Plasma clearance|K No urine collection required|K Overestimation of GFR in extracellular volume expansion|

||K Potential for increased precision|K Inaccurate values with 1-sample technique, particularly at|

|||lower GFR levels|

|||K Longer duration of plasma sampling required for low GFR|

|Nuclear imaging|K No urine collection or repeated|K Less accurate|

||blood samples required||

||K Relatively short duration||

|Markers|||

|Inulin|K Gold standard||

|Opportunistic finding or total protein strip result for albumin of positive reagent|Inspect urine|Yes|positive? reagent strip Repeat|No| |---|---|---|---|---|

||Cloudy?|Yes|Treat infection if positive MSU for C & S||

||No||||

|Patient requires testing|||||

|for proteinuria as part of CKD detectionor|Measure urinary ACR||||

|surveillance program|||||

||ACR > 300 mg/g|Yes|Severely increased||

||( > 30 mg/mmol)?||proteinuria||

||ACR ≥30 mg/g||||

|No|(≥3mg/mmol)?||||

||||Refer for specialist||

||Yes||assessment e.g., possible biopsy||

||Send 2 further EMU samples for ACR||||

||within the next 2 months||||

||||Yes||

||EMU||||

||(≥3 mg/mmol) in at|Yes|||

||least 1of 2||Hematuria?||

||subsequent||||

||samples?||||

||No||Moderately increased||

||||albuminuria||

||Continue routine|Continue routine|||

||observation||||

|Factor|Examples of effect| |---|---|

|Preanalytical factors||

|Transient elevation in albuminuria|Menstrual blood contamination|

||Symptomatic UTI 181|

||Exercise 182|

|Reference|Population| |---|---|

||||||GFR decline| |---|---|---|---|---|---|

||||Baseline GFR|Mean Follow-up|Mean (SD) or|

|MDRD Study|Study A: GFR 25-80 ml/min/1.73 m 2|28|Mean (SD)|1.2|3.7 (7.6)|

|Group 226|||37.1 (8.7)|||

||Study B: GFR 7.5-24 ml/min/1.73 m 2|63|15.0 (4.5)||4.3 (4.7)|

|Klahr S et al. 227|Study 1: GFR 25-55 ml/min/1.73 m 2||Mean (SD)|2.2 years||

||-Usual protein, usual MAP|145|37.6 (9.0)||4.5 (3.7 -5.3)|

||-Usual protein, low MAP|149|38.2 (8.6)||3.3 (2.5 -4.1)|

||-Low protein, usual MAP|140|38.9 (8.8)||3.3 (2.5 -4.2)|

||-Low protein, low MAP|151|39.7 (9.1)||2.3 (1.5 -3.0)|

||Study 2: GFR 13-45 ml/min/1.73 m 2|||||

||-Low protein, usual MAP|62|18.7 (3.1)||4.9 (3.8 -5.9)|

||-Low protein, low MAP|67|18.8 (3.3)||3.9 (3.2 -4.7)|

||-Very low protein, usual MAP|61|18.3 (3.7)||3.6 (2.8 -4.4)|

||-Very low protein, low MAP|65|18.4 (3.5)||3.5 (2.6 -4.5)|

|Wright J et al. 228|African Americans with||Mean (SD)|4 years|Mean (SE)|

||hypertension and|||||

||GFR 20-65 ml/min/1.73 m 2|||||

||-Low MAP|380|46.0 (12.9)||2.21 (0.17)|

||-Usual MAP|374|45.3 (13.2)||1.95 (0.17)|

||(GFR 30-59 ml/min/1.73 m 2 )||55.1 (50.8 -57.9)||1.03 ml/min/1.73 m 2 /year|

||GFR categories G3a-G5||29 (18-38)|2.9 years (1.3 -4.1)|0.35 ml/min/1.73 m 2 /year|

||(GFRo60 ml/min/1.73 m 2 )|||||

||GFR categories G3a-G5||33 ml/min/1.73 m 2|2.6 years|2.65 ml/min/1.73 m 2 /year|

||(GFRo60 ml/min/1.73 m 2 )|||(1.6-3.6)||

|||||||||||||||||Mortality:|Q1: 1.22 (1.06-1.41)|Q2: 1.05 (0.92-1.21)|Q3: Reference|Q4: 1.10 (0.96-1.27)||||||||||||| |---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

||Results (95% CI)|HR (multivariate):|No decline: 1.15 (0.99-1.24)|Mild: Reference|Moderate: 1.10 (0.98-1.30)|Severe: 1.54 (1.30-1.82)||HR (multivariate):|HF: 1.40 (1.20-1.65)|MI: 1.42 (1.14-1.76)|Stroke: 1.11 (0.89-1.37)|PAD: 1.67 (1.02-2.75)|||HR (multivariate):|CHD:|Q1: 1.30 (1.11-1.52)|Q2: 1.16 (1.00-1.35)|Q3: Reference|Q4: 1.04(0.90-1.22)|HR (multivariate):|All death: 1.45 (1.13-1.86)|CVD death: 2.48 (1.58-3.89)|CHD death: 2.14 (1.07-4.29)|Stroke death: 2.79 (1.45-5.36)|HR (multivariate):|All death: 1.73 (1.54-1.94)|CVD death: 1.70 (1.40-2.06)|||||

||Follow-up|5.7 yrs (median)||||||Subsequent|8 years after|enrollment in|year 7||||Up to Jan 1, 2006|(Baseline 1987-89)|||||Up to Dec 31,|2005|(Baseline 1989-94)|||Mean follow-up|9.9 yrs||||||

||Outcome|Death||||||Incident:|HF|MI|Stroke|PAD|||CHD & all|cause|mortality||||All cause,|CVD,|CHD,|& stroke|mortality|All cause,|& CVD|mortality|||||

|Categories for decline in|kidney function|No decline: eGFR 0 ml/min/yr|Mild decline: 0 to 1|Moderate decline: 1 to 4|Severe decline: 44|||Rapid decline: eGFR|43 ml/min/1.73 m 2 /yr|Not rapid decline:|r3 ml/min/1.73 m 2 /yr||||Quartiles of % annual|change in eGFR:|Q1 (-52.76 to -5.65)|Q2 (-5.65 to -0.47)|Q3 (-0.47 to -0.33)|Q4 (-0.33 to 42.94)|% decrease:|o20% decrease|Z20% decrease|||Rapid decline: eGFR|43 ml/min/1.73 m 2 /yr|Not rapid decline:|o3 ml/min/1.73 m 2 /yr||||

||N|4171||||||4378|||||||13,029||||||7968|||||4380|||||||

||Study population|Veterans Affairs|-GFR categories G3a|and G3b (GFR 30-59|ml/min/1.73 m 2 ) with|Z2 eGFR|measurements|Cardiovascular|Health Study|-Age 65þ|-eGFR|measurements at|baseline, years|3 and 7|ARIC study|-eGFR|measurements at|baseline and 3 years|||Taiwanese civil|servant & school|teachers|||Cardiovascular|Health Study|-Age 65þ|-eGFR|measurements at|baseline, years|3 and 7|

||Study|Al-Aly Z et al. 232||||||Shlipak et al. 233|||||||Matsushita et al. 221||||||Cheng et al. 234|||||Rifkin et al. 235|||||||

|Definition of|All-cause mortality|ESRD*| |---|---|---|

|progression|HR** (95% CI)|HR** (95% CI)|

|Certain rise|1.51 (1.46-1.56)|0.33 (0.26-0.42)|

|Uncertain rise|1.12 (1.08-1.16)|0.39 (0.30-0.51)|

|Stable (reference)|Ref|Ref|

|Uncertain drop|0.98 (0.95-1.01)|2.13 (1.84-2.47)|

|Certain drop|1.89 (1.83-1.95)|5.11 (4.56-5.71)|

|Absolute rate of change|Adjusted for eGFR at first|Adjusted eGFR at last creatinine| |---|---|---|

|(over a median of 3.5 years)|creatinine measurement HR** (95% CI)|measurement HR** (95% CI)|

|Increasing eGFR|0.64 (0.48-0.86)|1.20 (0.90-1.61)|

|Stable (0 ml/min/1.73 m 2 /year)|Ref|Ref|

|-1 ml/min/1.73 m 2 /year|2.05 (1.56-2.69)|1.45 (1.11-1.90)|

|-2 ml/min/1.73 m 2 /year|2.71 (2.08-3.53)|1.58 (1.21-2.06)|

|-3 ml/min/1.73 m 2 /year|3.98 (3.06-5.17)|1.63 (1.25-2.13)|

|-4 ml/min/1.73 m 2 /year|5.82 (4.45-7.61)|1.90 (1.45-2.48)|

|-5 ml/min/1.73 m 2 /year or more|12.49 (10.04-15.53)|1.70 (1.36-2.12)|

|Percentage Change:|||

|Increasing|0.76 (0.55-1.07)|1.11 (0.80 -1.55)|

|Stable|Ref|Ref|

|-1 to -2%/year|1.17 (0.81-1.68)|0.97 (0.67-1.40)|

|-3 to -4%/year|1.79 (1.25-2.56)|1.19 (0.83-1.71)|

|-5 to -6%/year|2.26 (1.55-3.29)|1.21 (0.83-1.78)|

|-7%/year or more|11.30 (8.53-14.97)|2.17 (1.60-2.93)|

|3.1.15: We recommend a target hemoglobin A 1c (HbA 1c )| |---|

|of B7.0% (53 mmol/mol) to prevent or delay|

|progression of the microvascular complications of|

|diabetes, including diabetic kidney disease. (1A)|

|3.1.16: We recommend not treating to an HbA 1c target of o7.0% (o53 mmol/mol) in patients at risk of|

|hypoglycemia. (1B)|

|3.1.17: We suggest that target HbA 1c be extended above|

|7.0% (53 mmol/mol) in individuals with comor-|

|bidities or limited life expectancy and risk of|

|hypoglycemia. (2C)|

|3.1.18: In people with CKD and diabetes, glycemic control|

|should be part of a multifactorial intervention|

|strategy addressing blood pressure control and|

|cardiovascular risk, promoting the use of angio-|

|tensin-converting enzyme inhibition or angio-|

|tensin receptor blockade, statins, and antiplatelet|

|therapy where clinically indicated. (Not Graded)|

|Study|Intensified treatment versus normal treatment HbA 1C goals|Albuminuria outcome| |---|---|---|

|ADVANCE 294|6.5% (48 mmol/mol) versus 7.3% (56 mmol/mol)|9% k in new ACR 3-30 mg/mmol (30-300 mg/g)|

|||30% k in ACR progression to 430 mg/mmol (4300 mg/g)|

Continued

Figure 13 | Meta-analysis of NRI for all-cause mortality, CVD mortality, and ESRD. NRI summarizes the risk of clinical outcomes among participants who are reclassified from one estimated GFR category using the MDRD Study equation to another estimated GFR category using the CKD-EPI equation compared with those who are not reclassified. NRI greater than zero favors the CKD-EPI equation. NRI less than zero favors the MDRD Study equation. The sizes of the data markers are proportional to the inverse of the variance of the NRIs. CKD-EPI, Performance comparison of creatinine-based GFR estimating equations outside of North America, Europe, and Australia

Strengths and limitations of GFR measurement methods and markers Requires standardization for 99m Tc K Dissociation and protein binding of 99m Tc K Concern for NSF when gadolinium is used as the tracer Abbreviations: DTPA, diethylenetriamine pentaacetic acid; EDTA, ethylenediamine tetraacetic acid; GFR, glomerular filtration rate; NSF, nephrogenic systemic fibrosis.

122ct infection, heart failure, other transitory illnesses, and strenuous exercise), especially in the case of type 1 diabetes present for less than 5 years.The presence of hematuria may indicate non-diabetic renal disease.This figure was published and adapted from Lamb EJ, Price CP.122Kidney function tests, in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, eds Burtis CA, Ashwood E, Bruns DE, 5 th edition, pp 669-708, 2012. Copyright Elsevier. -individual variability, and is required to exclude the diagnosis of orthostatic (postural) proteinuria. However, a random urine sample is acceptable if no EMU sample is available.

Decline in kidney function in CKD populations : CI, confidence interval; CKD, chronic kidney disease; GFR, glomerular filtration rate; IQR, interquartile range; MAP, mean arterial pressure; MDRD, Modification of Diet in Renal Disease; SD, standard deviation; SE, standard error.

Association between absolute and percentage change in kidney function and risk of ESRD*, based on adjustment for eGFR at the first and last measurement

has been updated in 2012. The first three recommendations below are reproduced verbatim from this guideline.

Prevalence of CKD complications by GFR category* derived from CKD cohorts

Hemoglobin thresholds used to define anemia

In making recommendations for therapeutic targets for mineral metabolism abnormalities, we have been careful not to reach beyond the evidence.

413mary data for bisphosphonates and CKD taken up enthusiastically by Arthur Osman412and further explored by Lyon et al. who conducted a form of crossover study of supplementation with bicarbonate in 17 people with moderate kidney failure and suggested that treatment with alkali might preserve kidney function.413Rustom et al. described a reduction in proximal renal tubular catabolism and markers of tubular injury after oral NaHCO 3 in 11 people with mild/moderate renal impairment (mean 51

11 ) tively constant across a broad range of baseline lowdensity lipoprotein cholesterol (LDL-C) levels 5. Optimal diabetes control HbA 1C o7% (53 mmol/mol) 6. Optimal BP control to o140/90 mm Hg or o130/80 mm Hg in those with CKD and depending on the degree of proteinuria (see Recommendations 3.1.4and 3.1.5)7. Aspirin is indicated for secondary prevention but not primary prevention 8. Correction of anemia to individualized targets (see KDIGO Clinical Practice Guideline for Anemia in CKD11 )

Peripheral arterial disease and CKD : ABI, ankle-brachial index; CHD, coronary heart disease; CI, confidence interval; CKD, chronic kidney disease; CrCl, creatinine clearance; d, day; GFR, glomerular filtration rate; HERS, Heart and Estrogen/Progestin Replacement Study; HR, hazard ratio; IQR, interquartile range; NHANES, National Health and Nutrition Examination Survey; PAD, peripheral arterial disease; PVD, peripheral vascular disease.attributed to the greater prevalence of traditional risk factors such as diabetes, hypertension, dyslipidemia, advanced age, and renal-specific factors.

7 he European Society of Urogenital Radiology (ESUR)611and the KDIGO Clinical Practice Guideine for Acute Kidney Injury.7

the importance of proteinuria in addition to low GFR in the risk of AKICKD and risk of hospitalization and mortalityRegardless of the method used to estimate GFR, hospitalization and mortality rates are higher in people with CKD. Exact rates vary with comorbidity and severity of CKD, and are not well-defined. Selection of interventions that could reduce hospitalizations, morbidity, mortality, and costs in people with CKD is not well-studied.

Figure 21 | Referral decision making by GFR and albuminuria. *Referring clinicians may wish to discuss with their nephrology service depending on local arrangements regarding monitoring or referring. GFR, glomerular filtration rate. Modified with permission from Macmillan Publishers Ltd: Kidney International. Levey AS, de Jong PE, Coresh J, et al.

673comes of early versus late referral Med, Chan MR, Dall AT, Fletcher KE, et al.673Outcomes in patients with chronic kidney disease referred late to nephrologists: a meta-analysis. 120: 1063-1070, 2007, with permission from Elsevier; accessed http://download.journals.elsevierhealth.com/pdfs/journals/0002-9343/PIIS000293430700664X.

Collaboration Among ParticipantsThe KDIGO Co-Chairs appointed the Work Group Co-Chairs, who then assembled the Work Group of domain experts, including individuals with expertise in internal medicine, adult and pediatric nephrology, diabetology/ endocrinology, clinical chemistry, and epidemiology.The Tufts Center for Kidney Disease Guideline Development and Implementation at Tufts Medical Center in Boston, Massachusetts, USA, was contracted to conduct systematic evidence review and provide expertise in guideline development methodology.The ERT consisted of physician-methodologists with expertise in nephrology, a project coordinator, a research assistant, and a medical writer-editor.The ERT instructed and advised Work Group members in all steps of literature review, critical literature appraisal, and guideline development.The Work Group and the ERT collaborated closely throughout the project.The Work Group and its Chairs, KDIGO Co-chairs, ERT, and KDIGO support staff met for three 2-day meetings for training in the guideline development process, topic discussion, and consensus development.

Topics of interest for the management of CKD guideline AKI, acute kidney injury; BP, blood pressure; CKD, chronic kidney disease; cys C, cystatin C; DM, diabetes mellitus; EDTA, ethylenediamine tetraacetic acid; ESRD, end-stage renal disease; GFR, glomerular filtration rate; HTN, hypertension; IDMS, isotope dilution mass spectrometry; KTR, kidney-transplant recipient; NA, not applicable; NFD, nephrogenic fibrosing dermopathy; QOL, quality of life; RCT, randomized controlled trial; RRT renalreplacement therapy; SCr, serum creatinine; SCysC, serum cystatin C; SR, systematic review; WG, Work Group. Accuracy specifically measured as the percentage of GFR estimates within 30% (P 30 ) of the measured GFR. Higher P 30 values reflect greater accuracy; values are decreased by both greater bias and worse precision.

Classification of study qualityGood qualityLow risk of bias and no obvious reporting errors, complete reporting of data.Must be prospective.If study of intervention, must be randomized controlled study.Fair qualityModerate risk of bias, but problems with study or paper are unlikely to cause major bias.If study of intervention, must be prospective.Poor qualityHigh risk of bias or cannot exclude possible significant biases. Poor methods, incomplete data, reporting errors. Prospective or retrospective.

Grading evidence and recommendations for clinical practice guidelines in nephrology. A position statement from Kidney Disease: Improving Global Outcomes (KDIGO). Kidney Int 2006; 70: 2058-2065; accessed http://www.nature.com/ ki/journal/v70/n12/pdf/5001875a.pdf Final grade for overall quality of evidence

: Merck; Otsuka Grant/Research Support: Abbott; Amgen; Canadian Institutes of Health Research; Genzyme, Kidney Foundation of Canada; Merck; Ortho Paul E Stevens, MB, FRCP (Work Group Co-Chair), is Consultant Nephrologist and Associate Medical Director, East Kent Hospitals University NHS Foundation Trust, Kent and Canterbury Hospital in the UK. He is a member of the Department of Health's Renal Advisory Group and Renal Pathology Group and immediate past-President of the British Renal Society. Dr Stevens established the Kent Kidney Care Centre, one of the largest general hospital renal units in the UK and served as a clinical advisor on NICE publications Anaemia Management in People with Chronic Kidney Disease and Chronic Kidney Disease: National Clinical Guideline for Early Identification and Management in Adults in Primary and Secondary Care. He is also Chair of NICE Quality Standards in Chronic Kidney Disease.

SUPPLEMENTARY MATERIAL

Supplemental Table 1 : Search strategy. Supplemental Table 2 : Equations based on serum creatinine assays in adults that are not traceable to the standard reference material. Supplemental Table 3 : Equations based on serum cystatin C assays in adults that are not traceable to standard reference material. Supplementary material is linked to the online version of the paper at http://www.kdigo.org/clinical_practice_guidelines/ckd. remain nephroprotective Beta-blockers K Reduce dose by 50% in people with GFR o30 ml/min/1.73 m 2 Digoxin K Reduce dose based on plasma concentrations 2. Analgesics NSAIDS K Avoid in people with GFR o30 ml/min/1.73 m 2 K Prolonged therapy is not recommended in people with GFR o60 ml/min/1.73 m 2 K Should not be used in people taking lithium K Avoid in people taking RAAS blocking agents Opioids K Reduce dose when GFR o60 ml/min/1.73 m 2 K Use with caution in people with GFR o15 ml/min/1.73 m 2 3. Antimicrobials Penicillin K Risk of crystalluria when GFR o15 ml/min/1.73 m 2 with high doses K Neurotoxicity with benzylpenicillin when GFR o15 ml/min/1.73 m 2 with high doses (maximum 6 g/day) Aminoglycosides K Reduce dose and/or increase dosage interval when GFR o60 ml/min/1.73 m 2 K Monitor serum levels (trough and peak) K Avoid concomitant ototoxic agents such as furosemide Macrolides K Reduce dose by 50% when GFR o30 ml/min/1.73 m 2 Fluoroquinolones K Reduce dose by 50% when GFR o15 ml/min/1.73 m 2 Tetracyclines K Reduce dose when GFR o45 ml/min/1.73 m 2 ; can exacerbate uremia Antifungals K Avoid amphotericin unless no alternative when GFR o60 ml/min/1.73 m 2 K Reduce maintenance dose of fluconazole by 50% when GFR o45 ml/min/1.73 m 2 K Reduce dose of flucytosine when GFR o60 ml/min/1.73 m 2 4. Hypoglycemics Sulfonylureas K Avoid agents that are mainly renally excreted (e. php K Avoid in people with suspected functional renal artery stenosis K Start at lower dose in people with GFR o45 ml/min/1.73 m 2 K Assess GFR and measure serum potassium within 1 week of starting or following any dose escalation K Temporarily suspend during intercurrent illness, planned IV radiocontrast administration, bowel preparation prior to colonoscopy, or prior to major surgery K Do not routinely discontinue in people with GFR o30 ml/min/1.73 m 2 as they remain nephroprotective Beta-blockers K Reduce dose by 50% in people with GFR o30 ml/min/1.73 m 2 Digoxin K Reduce dose based on plasma concentrations 2. Analgesics NSAIDS K Avoid in people with GFR o30 ml/min/1.73 m 2 K Prolonged therapy is not recommended in people with GFR o60 ml/min/1.73 m 2 K Should not be used in people taking lithium K Avoid in people taking RAAS blocking agents Opioids K Reduce dose when GFR o60 ml/min/1.73 m 2 K Use with caution in people with GFR o15 ml/min/1.73 m 2 3. Antimicrobials Penicillin K Risk of crystalluria when GFR o15 ml/min/1.73 m 2 with high doses K Neurotoxicity with benzylpenicillin when GFR o15 ml/min/1.73 m 2 with high doses (maximum 6 g/day) Aminoglycosides K Reduce dose and/or increase dosage interval when GFR o60 ml/min/1.73 m 2 K Monitor serum levels (trough and peak) K Avoid concomitant ototoxic agents such as furosemide Macrolides K Reduce dose by 50% when GFR o30 ml/min/1.73 m 2 Fluoroquinolones K Reduce dose by 50% when GFR o15 ml/min/1.73 m 2 Tetracyclines K Reduce dose when GFR o45 ml/min/1.73 m 2 ; can exacerbate uremia Antifungals K Avoid amphotericin unless no alternative when GFR o60 ml/min/1.73 m 2 K Reduce maintenance dose of fluconazole by 50% when GFR o45 ml/min/1.73 m 2 K Reduce dose of flucytosine when GFR o60 ml/min/1.73 m 2 4. Hypoglycemics Sulfonylureas K Avoid agents that are mainly renally excreted (e. g., glyburide/ glibenclamide) K Other agents that are mainly metabolized in the liver may need reduced dose when GFR o30 ml/min/1.73 m 2 (e.g., gliclazide, gliquidone) Insulin K Partly renally excreted and may need reduced dose when GFR o30 ml/min/1.73 m 2 Metformin K Suggest avoid when GFR o30 ml/min/1.73 m 2 , but consider risk-benefit if GFR is stable K Review use when GFR o45 ml/min/1.73 m 2 K Probably safe when GFR X45 ml/min/1.73 m 2 K Suspend in people who become acutely unwell

7. Anticoagulants

Low-molecular-weight heparins K Halve the dose when GFR o30 ml/min/1.73 m 2 K Consider switch to conventional heparin or alternatively monitor plasma anti-factor Xa in those at high risk for bleeding Warfarin K Increased risk of bleeding when GFR o30 ml/min/1.73 m 2 K Use lower doses and monitor closely when GFR o30 ml/min/1.73 m 2 8. Miscellaneous Lithium K Nephrotoxic and may cause renal tubular dysfunction with prolonged use even at therapeutic levels K Monitor GFR, electrolytes, and lithium levels 6 monthly or more frequently if the dose changes or the patient is acutely unwell K Avoid using concomitant NSAIDs K Maintain hydration during intercurrent illness K Risk-benefit of drug in specific situation must be weighed Abbreviations: ACE-I, angiotensin-converting enzyme inhibitor; ARB, angiotensin-receptor blocker; CKD, chronic kidney disease; GFR, glomerular filtration rate; NSAIDs, nonsteroidal anti-inflammatory drugs; RAAS, renin-angiotensin-aldosterone system; SCr, serum creatinine.

Balance between desirable and undesirable effects

The larger the difference between the desirable and undesirable effects, the more likely a strong recommendation is warranted. The narrower the gradient, the more likely a weak recommendation is warranted. Quality of the evidence

The higher the quality of evidence, the more likely a strong recommendation is warranted.

Values and preferences

The more variability in values and preferences, or more uncertainty in values and preferences, the more likely a weak recommendation is warranted. Costs (resource allocation)

The higher the costs of an intervention-that is, the more resources consumed-the less likely a strong recommendation is warranted.

Reproduced from Going from evidence to recommendations. Guyatt GH, Oxman AD, Kunz R, et al. 724 We also searched for pertinent existing guidelines and systematic reviews.

9. Recommendation grading criteria

Describe the criteria used to rate the quality of evidence that supports the recommendations and the system for describing the strength of the recommendations. Recommendation strength communicates the importance of adherence to a recommendation and is based on both the quality of the evidence and the magnitude of anticipated benefits and harms.

Quality of individual studies was graded in a three-tiered grading system (see Table 39 ). Quality of evidence (Table 40 ) was graded following the GRADE approach. Strength of the recommendation was graded in a two-level grading system which was adapted from GRADE for KDIGO with the quality of overall evidence graded on a four-tiered system (Tables 41 and 43 ).

The Work Group could provide general guidance in ungraded statements. 10. Method for synthesizing evidence

Describe how evidence was used to create recommendations, e.g., evidence tables, metaanalysis, decision analysis.

For systematic review topics, summary tables and evidence profiles were generated.

For recommendations on treatment interventions, the steps outlined by GRADE were followed.

11. Prerelease review

Describe how the guideline developer reviewed and/or tested the guidelines prior to release.

The guideline had undergone internal review by the KDIGO Board of Directors in January 2012 and external review in May 2012. Public review comments were compiled and fed back to the Work Group, which considered comments in its revision of the guideline. 12. Update plan State whether or not there is a plan to update the guideline and, if applicable, expiration date for this version of the guideline.

There is no date set for updating this entire guideline. The need for updating of the guideline will depend on the publication of new evidence that would change the quality of the evidence or the estimates for the benefits and harms. Results from registered ongoing studies and other publications will be reviewed periodically to evaluate their potential to impact on the recommendations in this guideline. Specific sections may be updated separately from the entire guideline within the next 3-5 years depending on the evidence base.

13. Definitions

Define unfamiliar terms and those critical to correct application of the guideline that might be subject to misinterpretation.

Acronyms and Abbreviations.

14. Recommendations and rationale

State the recommended action precisely and the specific circumstances under which to perform it. Justify each recommendation by describing the linkage between the recommendation and its supporting evidence. Indicate the quality of evidence and the recommendation strength, based on the criteria described in Topic 9.

Each guideline chapter contains recommendations for evaluation and management of CKD patients. Each recommendation builds on a supporting rationale with evidence tables if available. The strength of the recommendation and the quality of evidence are provided in parenthesis within each recommendation.

15. Potential benefits and harm

Describe anticipated benefits and potential risks associated with implementation of guideline recommendations.

The benefits and harm for each comparison of interventions is provided in summary tables and summarized in evidence profiles. The estimated balance between potential benefits and harm was considered when formulating the recommendations. The Work Group took on the primary role of writing the recommendations and rationale statements and retained final responsibility for the content of the guideline statements and the accompanying narrative. The ERT reviewed draft recommendations and grades for consistency with the conclusions of the evidence review.

Format for Guideline Recommendations

Each chapter contains one or more specific recommendations. Within each recommendation, the strength of recommendation is indicated as level 1 or level 2 and the quality of the supporting evidence is shown as A, B, C or D. The recommendation statements and grades are followed by the rationale and clarification of the wording of the statement, a brief background with relevant definitions of terms, and then a chain of logic which summarizes the key points of the evidence base and the judgments supporting the recommendation. Some sections also contain research recommendations in variable degrees of detail, suggesting future research to resolve current uncertainties.

Limitations of Approach

Although the literature searches were intended to be comprehensive, they were not exhaustive. MEDLINE was the only database searched. Hand searches of journals were not performed, and review articles and textbook chapters were not systematically searched. However, important studies known to domain experts that were missed by the electronic literature searches were added to the retrieved articles and reviewed by the Work Group.

Summary of the Review Process

Several tools and checklists have been developed to assess the quality of the methodological process for systematic review and guideline development. These include the Appraisal of Guidelines for Research and Evaluation (AGREE) criteria, 726 the Conference on Guideline Standardization (COGS) checklist, 727 and the Institute of Medicine's recent Standards for Systematic Reviews 728 and Clinical Practice Guidelines We Can Trust. 729 Portuguese and Spanish language in the area of nephrology and nutrition. His book Principles of Nephrology and Electrolyte Disturbances (Guanabara Koogan Group Gen, 2010) is on its 5 th Edition. He has more than 150 publications and has given more than 600 lectures locally and internationally. He is a past Board member and executive committee member of the ISN and is currently the Chairman of the ISN-Interventional Nephrology Committee. Dr Riella is a member of the editorial board of several medical journals, including as Associate Editor of Hemodialysis International and International Editor of Seminar in Dialysis for Interventional Nephrology. He is also President and founder of Pro-Renal Foundation of Brazil (www.pro-renal.org.br), a non-for-profit organization dedicated to patient assistance, CKD prevention and education, and supporting research in kidney and metabolic diseases. The Foundation provides free medical care to more than 1800 renal patients through a multidisciplinary team of physicians, nurses, psychologists, social workers, and dietitians. The Foundation is maintained by donations of the community and receives no public funds. Dr Riella is the past-President of the International Federation of Kidney Foundations (IFKF) 2009-2011. He is also the co-chairman of World Kidney Day, a joint project of IFKF and and ISN. He is a member of the Executive Committee of KDIGO, National Academy of Medicine in Brazil The recent work from his research group has been dedicated to finding early markers of kidney injury in the urine that will precede any detectable loss in kidney function. They will study these urine biomarkers in several populations, including the ambulatory elderly, HIV-infected men and women, and in population-based studies. The group believes that these injury markers hold promise both for understanding how various exposures impact the kidney, and also to forecast future declines in kidney failure.

Dr Shlipak reported no relevant financial relationships

Haiyan Wang, MD, is Professor of Medicine at Peking University First Hospital. She is the current President of Peking University Institute of Nephrology and the Vice Director, Academic Committee, Peking University Health Science Center and Member, Academic Degree Committee, Peking University Health Science Center.

Professor Wang is very active in the academic area of national and international nephrology and internal medicine. She was the Vice President of Chinese Medical Association (1999-2009) and the President of Chinese Society of Internal Medicine (2000-2008), as well as the President of Chinese Society of Nephrology (1992-1998). She has also served as the ISN Councilor member (2004-2008) training in internal medicine, nephrology, and rheumatology in Germany (Aachen University Hospital and Munich University Hospital) and the USA (Georgetown University Medical Center and Tufts Medical Center). Since 2001, she has been participating in or directing the evidence review for KDOQI and KDIGO guidelines. As Director of Guideline Development, Dr Uhlig has a substantial role in coordinating the ERT. She orchestrates and supervises the guideline development process and didactic curriculum that provides Work Group members with formal instruction on topics related to guideline development. As project director on individual guidelines, she directs and supervises the collection, evaluation, grading, and synthesis of evidence and the drafting and revisions of the final evidence report. She provides methodological guidance and training to Work Group members at meetings regarding topic refinement, key question formulation, data extraction, study assessment, evidence grading, and recommendation formulation. She provides nephrology expertise in the interpretation and review of guideline recommendations and evidence reports. In this capacity, A special debt of gratitude is owed to the KDIGO Co-Chairs Kai-Uwe Eckardt, Bertram Kasiske, David Wheeler, and the KDIGO Board for their invaluable guidance throughout the development of this guideline. In particular, we thank the ERT members: Katrin Uhlig, Dana Miskulin, Amy Earley, Shana Haynes, and Jenny Lamont for their substantial contribution to the rigorous assessment of the available evidence. We are also especially grateful to the Work Group members for their expertise throughout the entire process of literature review, data extraction, meeting participation, the critical writing and editing of the statements and rationale, which made the publication of this guideline possible. The generous gift of their time and dedication is greatly appreciated. The entire Work Group and its Co-Chairs would also like to extend a special debt of gratitude to Michael Cheung, who has committed time and energy above and beyond, to the formatting and proof reading of the completed manuscript. Without his help, we would have been hard pushed to complete this task. Finally, and on behalf of the Work Group, we gratefully acknowledge the careful assessment of the draft guideline by external reviewers. The Work Group considered all of the valuable comments made and where appropriate, suggested changes were incorporated into the final publication. The following individuals provided feedback during the public review of the

References

引用 / 出处

2012 KDIGO：CKD评估与管理临床实践指南. 2013.