Performance of Glomerular Filtration Rate Estimating Equations in Kidney Transplant Recipients of Various Races: A Retrospective Cohort Study.

Background: We assessed the accuracy of different GFR estimating equations in kidney transplant recipients across diverse racial backgrounds, addressing the previously identified validation gap in multiethnic populations predominantly studied in White cohorts.

Methods: In this single-center study, eGFR was compared to the measured GFR (mGFR) one year following kidney transplantation.

Results: The 1-year eGFR and mGFR data from 1145 participants (54% Whites, 23% Hispanics, 9% Blacks, 7% Native Americans, and 6% Asians) revealed varied correlations across racial groups. For Whites, the combined 2021 CKD-EPI creatinine-cystatin C formulas demonstrated a stronger correlation (r = 0.72, [0.65, 0.78]) compared to the 2021 CKD-EPI creatinine and EKFC cystatin C equation. This equation also achieved the highest accuracy (P30: 77.1%). In Black recipients, both the 2009 CKD-EPI (r = 0.56 [0.42, 0.68]) and the 2021 CKD-EPI creatinine (r = 0.56 [0.41, 0.68]) exhibited modest correlations. The 2021 CKD-EPI creatinine-cystatin C equation showed improved correlation (r = 0.63 (0.43, 0.77)] and an accuracy of 62.7% (P30), which was slightly lower than the EKFC cystatin C equation (P30: 64.7%). However, neither the EKFC (rescaled) cystatin C nor the race-free kidney-specific equations outperformed existing eGFR equations for Black participants In Hispanic patients, combined creatinine-cystatin C equations outperformed creatinine-only equations. Among Native Americans, the combined creatinine-cystatin, EKFC (rescaled) cystatin C, and race-free kidney-specific equations achieved an accuracy rate exceeding 85%. In Asians, the CKD-EPI creatinine-cystatin C equation showed the highest correlation, while the race-free kidney-specific equation had the most accuracy.

Conclusion: Our findings indicate that creatinine-cystatin C combined equations outperformed single-marker formulas across all racial groups, with negligible differences between the 2009 CKD EPI and the race-neutral 2021 CKD-EPI version.