Abstract
BackgroundChronic kidney disease (CKD) diagnosis relies on glomerular filtration rate (eGFR) estimation, traditionally using the creatinine-based Modification of Diet in Renal Disease (MDRD) equation. The Chronic Kidney Disease Epidemiology Collaboration (CKDEPI) equation performs better in estimating eGFR and predicting mortality and CKD progression risk. Cystatin C is an alternative glomerular filtration marker less influenced by muscle mass. CKD risk stratification is improved by combining creatinine eGFR with cystatin C and urinary albumin to creatinine ratio (uACR). We aimed to identify the impact of introducing CKDEPI and cystatin C on the estimated prevalence and risk stratification of CKD in England and to describe prevalence and associations of cystatin C.Methods and FindingsCross sectional study of 5799 people in the nationally representative 2009 and 2010 Health Surveys for England. Primary outcome measures: prevalence of MDRD, CKDEPI and cystatin C-defined eGFR<60ml/min/1.73m2; prevalence of CKD biomarker combinations (creatinine, cystatin C, uACR). Using CKDEPI instead of MDRD reduced the prevalence of eGFR<60ml/min/1.73m2 from 6.0% (95% CI 5.4–6.6%) to 5.2% (4.7–5.8%) equivalent to around 340,000 fewer individuals in England. Those reclassified as not having CKD evidenced a lower risk profile. Prevalence of cystatin C eGFR<60ml/min/1.73m2 was 7.7% and independently associated with age, lack of qualifications, being an ex-smoker, BMI, hypertension, and albuminuria. Measuring cystatin C in the 3.9% people with CKDEPI-defined eGFR<60ml/min/1.73m2 without albuminuria (CKD Category G3a A1) reclassified about a third into a lower risk group with one of three biomarkers and two thirds into a group with two of three. Measuring cystatin C in the 6.7% people with CKDEPI eGFR >60ml/min/1.73m2 with albuminuria (CKD Category G1-2) reclassified almost a tenth into a higher risk group.LimitationsCross sectional study, single eGFR measure, no measured (‘true’) GFR.ConclusionsIntroducing the CKDEPI equation and targeted cystatin C measurement reduces estimated CKD prevalence and improves risk stratification.
Highlights
The 2012 Kidney Disease Improving Global Outcomes (KDIGO) recommendations advocate the routine use of the CKDEPI equation for reporting of estimated glomerular filtration rate (eGFR) as do the recently revised Chronic kidney disease (CKD) guidelines from the UK National Institute of Health and Care Excellence (NICE).[11,12]In a large retrospective study of routine creatinine requests, O’Callaghan et al showed that routine use of CKDEPI serum creatinine (Scr) equation in place of Modification of Diet in Renal Disease (MDRD) in a UK clinical biochemistry laboratory would result in a lower overall prevalence of CKD, but an increase in higher risk CKD stage 3–5 among older people.[13]
Effect on estimated prevalence of introducing new measures of kidney function Use of the CKDEPI Scr equation classified fewer individuals as having eGFR
People reclassified by CKDEPI as not having eGFR
Summary
The introduction in 2002 of a definition and classification system for chronic kidney disease (CKD) based on estimated glomerular filtration rate (eGFR) created a need for accurate methods to estimate GFR; subsequently the Modification of Diet in Renal Disease (MDRD) estimating equation was adopted worldwide.[1,2,3,4] In the UK, the National Service Framework for Renal Services 2004/05 led to national reporting of eGFR by clinical biochemistry laboratories from 2006 [5]; the General Practice pay for performance Quality Outcomes Framework (QOF) included targets for CKD management from 2006/07 [6]; and the NHS Vascular Checks Programme, introduced in 2009, includes screening for CKD (stage 3–5) in people aged 35–74 with newly identified type 2 diabetes or hypertension.[7] concern has been expressed that these methods of CKD classification and identification have resulted in over-diagnosis and unnecessary disease-labelling and treatment, especially in the elderly.[8]. We aimed to identify the impact of introducing CKDEPI and cystatin C on the estimated prevalence and risk stratification of CKD in England and to describe prevalence and associations of cystatin C
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