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)

Background: The Chronic Kidney Disease Epidemiology Collaboration equation for estimation of glomerular filtration rate (eGFR_CKD-EPI) improves GFR estimation compared with the Modification of Diet in Renal Disease Study equation (eGFR_MDRD) 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 eGFR_CKD-EPI and eGFR _MDRD. Outcomes of interest were all-cause and cardiovascular disease (CVD) mortality. Improvement in risk categorization with eGFR_CKD-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 eGFR _CKD-EPI, reducing the proportion of prevalent CKD classified as stage 35 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 eGFR _MDRD 3059 ml/min/1.73 m², 19.4% were reclassified to eGFR_CKD-EPI 6089 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 eGFR_MDRD >60 ml/ min/1.73 m ², 0.5% were reclassified to lower eGFR_CKD-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 eGFR _CKD-EPI; NRI was 0.21 for all-cause mortality (p<0.001) and 0.22 for CVD mortality (p<0.001). Conclusions: eGFR_CKD-EPI categories improve mortality risk stratification of individuals in the US population. If eGFR_CKD-EPI replaces eGFR_MDRD in the US, it will likely improve risk stratification.