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What is the best glomerular filtration marker to identify people with chronic kidney disease most likely to have poor outcomes?

BMJ 2015; 350 doi: http://dx.doi.org/10.1136/bmj.g7667 (Published 12 January 2015) Cite this as: BMJ 2015;350:g7667
  1. E J Lamb, consultant clinical scientist1,
  2. P E Stevens, consultant nephrologist2,
  3. J J Deeks, professor of biostatistics3
  1. 1Clinical Biochemistry, East Kent Hospitals University NHS Foundation Trust, Canterbury, CT1 3NG, UK
  2. 2Kent Kidney Care Centre, East Kent Hospitals University NHS Foundation Trust, Canterbury
  3. 3Test Evaluation Research Group, School of Health and Population Sciences, Public Health Building, University of Birmingham, Birmingham B15 2TT, UK
  1. Correspondence to: E Lamb elamb{at}nhs.net

Introduction

Glomerular filtration rate (GFR) is widely regarded as the best overall measure of kidney function. In recent years, the importance of this measure has increased as it has been incorporated as the primary criterion in an international classification system for kidney disease.1 Routine availability of GFR estimates has improved recognition of chronic kidney disease,2 3 but knowledge of GFR alone is insufficient to predict the risk of adverse outcomes in patients. Concern exists that not all people with decreased GFR, especially those without albuminuria, are at increased risk of adverse outcomes related to chronic kidney disease.4 This may cause unnecessary alarm to patients and waste healthcare resources. Outcomes of importance in chronic kidney disease include progressive loss of kidney function (including kidney failure), acute kidney injury, cardiovascular events, complications related to progression of chronic kidney disease, and mortality. Earlier studies concentrated on the relative accuracy of estimated GFR (eGFR) compared with “true” GFR.5 However, absolute accuracy in GFR estimation may not be the prime criterion, and some more recent literature has focused on the relative ability of different equations and markers to predict disease progression and poor outcomes.

GFR is measured using reference procedures that follow the renal clearance of an infused exogenous substance (such as inulin). However, these methods are cumbersome, impractical, and too costly for widespread use. Clinical laboratories report eGFR by using equations based on measurement of serum creatinine concentration, taking into account other variables including age, sex, and ethnicity. Laboratories use various equations to estimate GFR. Although perhaps not of primary interest to most requesting clinicians, the choice of equation can affect both the prognostic power and the accuracy of the GFR estimate. The Modification of Diet in Renal Disease (MDRD) Study equation has been widely used since 2000 to estimate GFR, …

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