Exploration of Chronic Kidney Disease Prevalence Estimates Using New Measures of Kidney Function in the Health Survey for England

BACKGROUND Chronic 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 FINDINGS Cross 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<60 ml/min/1.73 m(2); prevalence of CKD biomarker combinations (creatinine, cystatin C, uACR). Using CKDEPI instead of MDRD reduced the prevalence of eGFR<60 ml/min/1.73 m(2) 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<60 ml/min/1.73 m(2) 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<60 ml/min/1.73 m(2) 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 >60 ml/min/1.73 m(2) with albuminuria (CKD Category G1-2) reclassified almost a tenth into a higher risk group. LIMITATIONS Cross sectional study, single eGFR measure, no measured ('true') GFR. CONCLUSIONS Introducing the CKDEPI equation and targeted cystatin C measurement reduces estimated CKD prevalence and improves risk stratification.