For a study, it was determined how the unknown integrating race in the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation affects clinical trial screening, recruitment, and results. After calculating eGFR using the 2009 CKD-EPI creatinine equation with and without a race-specific coefficient or the 2021 CKD-EPI creatinine equation, the inclusion and outcomes of participants in the Canagliflozin and Renal Events in Diabetes with Established Nephropathy Clinical Evaluation (CREDENCE) trial, which randomized patients with type 2 diabetes and CKD to canagliflozin or placebo, were evaluated. For eGFR slope, proportional hazards models and piecewise linear mixed-effects models were used to evaluate treatment effects.
There were 2,931 (67%) White participants, 224 (5%), Black individuals, 877 (20%) Asian participants, and 369 (8%) other race people among the 4401 randomized participants. Recalculating screening eGFR without a race-specific coefficient among randomized participants had no influence on the chance of non-Black patients satisfying inclusion requirements, but would have eliminated 22 (10%) randomized Black people with eGFR30 ml/min per 1.73 m^2. Recalculation using the 2021 equation would have omitted eight (4%) Black patients for low eGFR and one (0.4%) Black person for eGFR90 ml/min per 1.73 m2, respectively, whereas 30 (0.7%) and 300 (7%) non-Black participants were excluded for low and high eGFR, respectively. Patients who would have been eliminated following recalculation using the race-free 2009 equation but not when recalculated using the 2021 equation had a significant proportion of endpoints (8 of 22; 36%) in Black patients (1 of 8; 13%). Following recalculation with either equation, the cardiovascular and renal therapy effects were consistent across eGFR categories. The changes in projected treatment effects on eGFR slope were minor, but qualitatively higher after recalculation using the 2021 equation. However, the effect of canagliflozin on chronic change in eGFR was reduced by 7% among Black patients while increasing by 6% among non-Black patients.
eGFR recalculation without the race-specific coefficient showed minor but possibly significant effects on event rates and the proportional number of Black patients in the CREDENCE trial, without significantly affecting effectiveness estimates.