The Implication of Dropping Race from the MDRD Equation to Estimate GFR in an African American-Only Cohort

Abstract

The widely used Modification of Diet in Renal Disease (MDRD) formula adapts a 1.212 multiplier for individuals who are identified as African Americans (AAs) or Blacks, which leads to a higher GFR estimation. As it stands, AAs have a lower prevalence of chronic kidney disease (CKD) but higher incidence of end-stage renal disease (ESRD) compared with Whites. Many hypotheses have been postulated to explain this paradox, but the imprecision of the GFR estimation with race-adaptation could be contributory. We performed a single-center, longitudinal, retrospective study on a cohort of outpatient AA patients using the MDRD and MDRDrace removed and CKD-EPI and CKD-EPIrace removed and their progression to CKD G5 (eGFR <15 ml/min/1.73 m2). 327 patients were analyzed. Median follow-up was 88.1 months (interquartile range, 34.4–129.1). When race was removed from MDRD, 39.9% of patients in CKD G1/2 were reclassified to CKD G3a, 72.6% of patients in CKD G3a would be reclassified to CKD G3b, and 54.1% and 36.4% of patients would be reclassified from CKD 3b to CKD G4 and CKD G4 to CKD G5, respectively $\left(p<0.0001\right)$ . Comparing the CKD-EPI formula against the MDRD in our cohort, we found that 8.2%, 18.8%, and 11.4% of patients were reclassified from CKD G1/2 to CKD G3a, CKD G3a to G3b, and CKD G3b to CKD G4 respectively. Overall median time to progression to CKD G5 was 137.4 (131.9–142.8) months in patients who were not reclassified and 133.6 (127.6–139.6) months for patients who were reclassified by MDRDrace removed $\left(p<0.288\right)$ . Concerns of inequitable access to healthcare have elicited calls to review race-corrected eGFR equations. A substantial number of individuals would have their CKD stage reclassified should have the MDRDrace removed equation be adopted en masse on an AA-only population. The discrepancy is highest at the 45–59 and >60 ml/min/1.72 min2 ranges. This will have tremendous impact on our center’s approach to pharmacological dosing, referral system, best practices, and outcome surveillance. Comprehensive review of the current “race-corrected” eGFR will require a multifaceted approach and adjunctive use of noncreatinine-based approach.