Clinical risk implications of the CKD epidemiology collaboration (CKD-EPI) equation compared with the Modification of Diet in Renal Disease (MDRD) study equation for estimated GFR

Background: The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) creatinine-based equation for estimated glomerular filtration rate (eGFR) is more accurate than the MDRD (Modification of Diet in Renal Disease) Study equation. However, it has not been determined whether the improvement in risk categorization applies to all segments of the population. Study Design: Population-based cohort study. Setting & Participants: Adults (aged <18 years) who did not have kidney failure at baseline and had at least one serum creatinine measurement and dipstick proteinuria evaluation in a province-wide laboratory registry from Alberta, Canada, in 2002-2007 (N = 1,010,988). Predictor: eGFR categories of <90, 60-89, 45-59, 30-44, and 15-29 mL/min/1.73 m ². Outcomes: All-cause mortality, acute myocardial infarction, end-stage renal disease, and doubling of serum creatinine level. Measurements: GFR was estimated by the CKD-EPI and MDRD Study equations. Results: The CKD-EPI equation reclassified 22.6% and 1.2% of participants to a higher and lower eGFR category, respectively, and decreased the prevalence of CKD stages 3 and 4 from 9.2% to 7.3%. Of 70,071 participants with eGFR _MDRD of 45-59 mL/min/1.73 m ², 30.8% were reclassified to eGFR _CKD-EPI of 60-89 mL/min/1.73 m ², and after adjusting for potential confounders, participants reclassified had a lower risk of all-cause mortality (incidence rate ratio [IRR], 0.77; 95% CI, 0.69-0.86), acute myocardial infarction (IRR, 0.73; 95% CI, 0.60-0.88), end-stage renal disease (IRR, 0.55; 95% CI, 0.32-0.94), and doubling of creatinine level (IRR, 0.78; 95% CI, 0.59-1.04) compared with those not reclassified. Similar findings were observed for those reclassified to a higher eGFR category from other eGFR _MDRD categories. Net reclassification improvements based on eGFR categories were positive for all outcomes (range, 0.146-0.256; all P < 0.001). Limitations: Relatively short follow-up (median, 2.8 years), lack of data for some potential confounders (eg, smoking), and mainly white participants. Conclusions: These results suggest that the CKD-EPI equation more accurately categorizes individuals regarding clinical risk than the MDRD Study equation.