Comparative Performance of the CKD Epidemiology Collaboration (CKD-EPI) and the Modification of Diet in Renal Disease (MDRD) Study Equations for Estimating GFR Levels Above 60 mL/min/1.73 m2

Abstract

Background The MDRD Study equation underestimates measured GFR at levels greater than 60 ml/min per 1.73 m2, with variable accuracy among subgroups; consequently estimated GFR (eGFR) ≥ 60 ml/min/1.73 m2 is not reported by clinical laboratories. Here, the performance of a more accurate GFR estimating equation, the CKD-EPI equation, is reported by level of GFR and clinical characteristics. Study Design Test of diagnostic accuracy Setting and Participants Pooled dataset of 3896 people from 16 studies with measured GFR (not used for development of either equation). Subgroups were defined by eGFR, age, sex, race, diabetes, prior solid organ transplant, and body mass index. Index Tests eGFR from the CKD-EPI and MDRD Study equations and standardized serum creatinine Reference Test Measured GFR using urinary or plasma clearance of exogenous filtration markers Results Mean (SD) measured GFR was 68 (36) ml/min/1.73 m2. For eGFR less than 30 ml/min/1.73 m2, both equations have similar bias (median difference compared to measured GFR). For eGFR between 30-59 ml/min/1.73 m2, bias was reduced from 4.9 to 2.1 ml/min/1.73 m2 (57% improvement). For eGFR between 60-89 ml/min/1.73 m2, bias was reduced from 11.9 to 4.2 ml/min/1.73 m2 (61 % improvement). For eGFR between 90-119 ml/min/1.73 m2, bias was reduced from 10.0 to 1.9 ml/min/1.73 m2 (75% improvement). Similar or improved performance was noted for most subgroups with eGFR < 90 ml/min/1.73 m2, other than BMI less than 20 kg/m2, with greater variation noted for some subgroups with eGFR ≥ 90 ml/min/1.73 m2. Limitations Limited number of elderly people and racial and ethnic minorities with measured GFR. Conclusions The CKD-EPI equation is more accurate than the MDRD Study equation overall and across most subgroups. In contrast to the MDRD Study equation, eGFR ≥ 60 ml/min/1.73 m2 can be reported using the CKD-EPI equation.