Purpose: New estimated glomerular filtration rate (eGFR) equations using serum creatinine (Cr) and/or cystatin C (CysC) have been derived to eliminate adjustment by perceived Black ancestry.  We sought to analyze the performance of newer eGFR equations in Black living kidney donor (LD) candidates.

Methods: Black LD candidates (n=64) who had measured iothalamate (i)GFR  between 1/2015 and 10/2021 were included, and eGFR was calculated using race adjusted (Cr2009, Cr-CysC2012) and race unadjusted (Cr2021, Cr-CysC2021) CKD-EPI equations.  Bias (eGFR-iGFR) and accuracy (percent within 30% of iGFR) were calculated.

Results: Mean age at LD evaluation was 41±12 yrs, and 45% were male.  Mean iGFR was 105±23 ml/min/1.73m².  Results are shown in Table 1.

CKD-EPICr2021 eGFR showed a greater negative bias, and underestimated iGFR to a level < 80 ml/min/1.73m² in 11% with iGFR ≥ 80.  Alternatively, the CKD-EPICr-CysC2021 equation showed less bias and high accuracy in the absence of correction for Black ancestry.  In donor candidates with iGFR ≥ 80 ml/min/1.73m², none were estimated below 80 by the CKD-EPICr-CysC2021 equation. Eighteen Black candidates went on to donate and had eGFR measured at 6-18 months post-donation.  By the Cr2021 equation, substantially more donors had an eGFR < 60 ml/min/1.73m² (44%), Table 2.

Conclusions: The CKD-EPICr2021 equation appears to underestimate true GFR in Black LD candidates, with the potential to exclude some for falsely low eGFR, and the potential to underestimate GFR post-donation.  Alternatively, the recently recalibrated CKD-EPICr-CysC2021 equation appears to perform well in Black LD candidates, without negative bias or underestimation.