Comparison of 2021 CKD-EPI Equations for Estimating Racial Differences in Preemptive Waitlisting for Kidney Transplantation

Background and objectives Wait time for kidney transplantation can accrue when GFR is <= 20 ml/min. We examined whether using the race-free 2021 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations to guide preemptive waitlisting could attenuate racial differences in accruable preemptive wait time. Design, setting, participants, & measurements Our retrospective cohort study included Black or White Chronic Renal Insufficiency Cohort (CRIC) participants who were theoretically eligible for waitlist registration. We used Weibull accelerated failure time models to determine the association between race (Black or White) and time to kidney failure from the qualifying visit when the eGFR by creatinine or creatinine-cystatin C 2021 CKD-EPI equations fell to <= 20 ml/min per 1.73 m(2). We then tested for differences in the time ratios from models using the 2021 creatinine- or creatinine-cystatin C-based CKD-EPI equation through a bootstrapping approach. Results By the creatinine equation, 472 CRIC participants were theoretically eligible for waitlist registration, and potential preemptive wait time was similar for Black versus White participants (time ratio, 1.05; 95% confidence interval, 0.81 to 1.35). The median wait time by the creatinine equation that could be accrued for Black participants was 23 versus 22 months in White participants. By the creatinine-cystatin C equation, 441 CRIC participants were eligible, and potential wait time was 20% shorter (95% confidence interval, 0.62 to 1.02) for Black than White participants. The median wait time that could be accrued for Black participants was 21 versus 26 months for White participants when using the creatinine-cystatin C equation. Using bootstrapping, the ratio of the time ratio of the models using the creatinine versus creatinine-cystatin C equation was statistically significantly different (ratio of the time ratios = 1.31 with 95% confidence interval, 1.06 to 1.62). Conclusions Use of the 2021 creatinine-based CKD-EPI equation to determine preemptive waitlist eligibility reduced racial differences in preemptive wait time accrual more than use of the creatinine-cystatin C2021 CKD-EPI equation within a theoretical context.