Importance: Living kidney donation is associated with increased long-term risk of end-stage renal disease (ESRD). An early postdonation marker of ESRD risk could improve postdonation risk assessment and counseling for kidney donors and allow early intervention for donors at increased risk. Objective: To determine the association between renal function in the first 6 months postdonation and subsequent risk of ESRD in kidney donors. Design, Setting, and Participants: This secondary analysis of a prospective national cohort uses a population-based registry of all living kidney donors in the United States between October 26, 1999, and January 1, 2018, with follow-up through December 31, 2018. All kidney donors who had donated in the date range and had serum creatinine measured at 6 months (±3 months) postdonation were included. Exposures: Renal function as measured by estimated glomerular filtration rate 6 months after donation (eGFR6). Main Outcomes and Measures: End-stage renal disease, ascertained via linkage to Centers for Medicare & Medicaid Services data. Results: A total of 71468 living kidney donors were included (of 109065 total donors over this period). Their median (interquartile range) eGFR6 was 63 (54-74) mL/min/1.73 m2. Cumulative incidence of ESRD at 15 years postdonation ranged from 11.7 donors per 10000 donors with eGFR6 values greater than 70 mL/min/1.73 m2 to 33.1 donors per 10000 donors with eGFR6 values of 50 mL/min/1.73 m2 or less. Adjusting for age, race, sex, body mass index, and biological relationship, every 10 mL/min/1.73 m2 reduction in eGFR6 was associated with a 28% increased risk of ESRD (adjusted hazard ratio, 1.28 [95% CI, 1.06-1.54]; P =.009). The association between predonation eGFR and ESRD was not significant and was fully mediated by eGFR6 (adjusted hazard ratio, 1.00 [95% CI, 0.86-1.17]; P =.97). The postdonation eGFR value was a better marker of ESRD than eGFR decline after donation or the ratio of eGFR6 to predonation eGFR, as determined by the Akaike information criterion (in which a lower value indicates a better model fit; eGFR6, 1495.61; predonation eGFR - eGFR6, 1503.58; eGFR6 / predonation eGFR, 1502.30). Conclusions and Relevance: In this study, there was an independent association of eGFR6 with subsequent ESRD risk in living kidney donors, even after adjusting for predonation characteristics. The findings support measurement of early postdonation serum creatinine monitoring in living kidney donors, and the use of these data to help identify donors who might need more careful surveillance and early intervention.
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