Comparison of the CKD Epidemiology Collaboration (CKD-EPI) and Modification of Diet in Renal Disease (MDRD) study equations: risk factors for and complications of CKD and mortality in the Kidney Early Evaluation Program (KEEP)

Background: The National Kidney Foundation has recommended that the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation replace the Modification of Diet in Renal Disease (MDRD) Study equation. Before implementing this change in the Kidney Early Evaluation Program (KEEP), we compared characteristics of reclassified individuals and mortality risk predictions using the new equation.

Methods: Of 123,704 eligible KEEP participants, 116,321 with data available for this analysis were included. Glomerular filtration rate (GFR) was estimated using the MDRD Study (eGFR(MDRD)) and CKD-EPI (eGFR(CKD-EPI)) equations with creatinine level calibrated to standardized methods. Participants were characterized by eGFR category: >120, 90-119, 60-89, 45-59, 30-44, and <30 mL/min/1.73 m(2). Clinical characteristics ascertained included age, race, sex, diabetes, hypertension, coronary artery disease, congestive heart failure, cerebrovascular disease, peripheral vascular disease, and anemia. Mortality was determined over a median of 3.7 years of follow-up.

Results: The prevalence of eGFR(CKD-EPI) <60 mL/min/1.73 m(2) was 14.3% compared with 16.8% using eGFR(MDRD). Using eGFR(CKD-EPI), 20,355 participants (17.5%) were reclassified to higher eGFR categories, and 3,107 (2.7%), to lower categories. Participants reclassified upward were younger and less likely to have chronic conditions, with a lower risk of mortality. A total of 3,601 deaths (3.1%) were reported. Compared with participants classified to eGFR of 45-59 mL/min/1.73 m(2) using both equations, those with eGFR(CKD-EPI) of 60-89 mL/min/1.73 m(2) had a lower mortality incidence rate (6.4 [95% CI, 5.1-7.7] vs 18.5 [95% CI, 17.1-19.9]). Results were similar for all eGFR categories. Net reclassification improvement was 0.159 (P < 0.001).

Conclusions: The CKD-EPI equation reclassifies people at lower risk of CKD and death into higher eGFR categories, suggesting more accurate categorization. The CKD-EPI equation will be used to report eGFR in KEEP.