Comparing the association of GFR estimated by the CKD-EPI and MDRD study equations and mortality: the third national health and nutrition examination survey (NHANES III) examination survey (NHANES III).
ABSTRACT: Background & Objectives The Chronic Kidney Disease Epidemiology Collaboration equation for estimation of glomerular filtration rate (eGFRCKD-EPI) improves GFR estimation compared with the Modification of Diet in Renal Disease Study equation (eGFRMDRD) but its association with mortality in a nationally representative population sample in the US has not been studied. METHODS: We examined the association between eGFR and mortality among 16,010 participants of the Third National Health and Nutrition Examination Survey (NHANES III). Primary predictors were eGFRCKD-EPI and eGFRMDRD. Outcomes of interest were all-cause and cardiovascular disease (CVD) mortality. Improvement in risk categorization with eGFRCKD-EPI was evaluated using adjusted relative hazard (HR) and Net Reclassification Improvement (NRI). RESULTS: Overall, 26.9% of the population was reclassified to higher eGFR categories and 2.2% to lower eGFR categories by eGFRCKD-EPI, reducing the proportion of prevalent prevalence of CKD classified as stage 3-5 from 45.6% to 28.8%. There were 3,620 deaths (1,540 from CVD) during 215,082 person-years of follow-up (median, 14.3 years). Among those with eGFRMDRD 30-59 ml/min/1.73 m2, 19.4% were reclassified to eGFRCKD-EPI 60-89 ml/min/1.73 m2 and these individuals had a lower risk of all-cause mortality (adjusted HR, 0.53; 95% CI, 0.34-0.84) and CVD mortality (adjusted HR, 0.51; 95% CI, 0.27-0.96) compared with those not reclassified. Among those with eGFRMDRD >60 ml/min/1.73 m2, 0.5% were reclassified to lower eGFRCKD-EPI and these individuals had a higher risk of all-cause (adjusted HR, 1.31; 95% CI, 1.01-1.69) and CVD (adjusted HR, 1.42; 95% CI, 1.01-1.99) mortality compared with those not reclassified. Risk prediction improved with eGFRCKD-EPI; NRI was 0.21 for all-cause mortality (p<0.001) and 0.22 for CVD mortality (p<0.001). CONCLUSIONS: eGFRCKD-EPI categories improve mortality risk stratification of individuals in the US population. If eGFRCKD-EPI replaces eGFRMDRD in the US, it will likely improve risk stratification.