Analysis of Estimated and Measured Glomerular Filtration Rates and the CKD-EPI Equation Race Coefficient in the Chronic Renal Insufficiency Cohort Study.

Zelnick et al1 analyzed data from the Chronic Renal Insufficiency Cohort (CRIC) obtained from the National Institute of Diabetes and Digestive and Kidney Diseases central repository and reported that the Chronic Kidney Disease-Epidemiology (CKD-EPI) equation estimated glomerular filtration rates (eGFR) were higher than iothalamate clearance glomerular filtration rates (iGFR) among self-reported Black participants with iGFR less than 45 mL/min/1.73 m2. Using the CKD-EPI equation without a (Black vs non-Black) race coefficient appeared to attenuate the difference between eGFR and iGFR (eGFR − iGFR). The authors suggested that the latter approach should be used more widely in clinical practice. We believe that examining potential bias in eGFR values within subgroups defined by iGFR is problematic. An unbiased eGFR estimation aims to ensure that for the set of individuals who have the same eGFR value, the mean iGFR value is the same as the eGFR. The correlation between the difference between eGFR and iGFR (eGFR − iGFR) and iGFR is expected for an unbiased eGFR estimation.2 We offer an alternative view of the data here with different clinical implications.