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)

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.

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).

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 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 eGFR_MDRD 30–59 ml/min/1.73 m², 19.4% were reclassified to eGFR_CKD-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 eGFR_MDRD >60 ml/min/1.73 m², 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).

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.