As of May 2012 over 92,000 patients were awaiting a solitary kidney transplant in the United States and new waitlist registrations have been steadily rising for over a decade. The increasing demand for transplantations and the decreasing availability of donor organs makes it imperative that organ allocation be as efficient and effective as possible. We performed a retrospective cohort study of adult recipients in the US (n=109,392) using SRTR data. The primary aim of the study was to evaluate the interaction of donor risk with recipient characteristics on post-transplant outcomes. Donor quality (based on kidney donor risk index [KDRI]) had significant interactions by race, primary diagnosis, and age. The hazard of a one unit increase in KDRI on overall graft loss in non-African Americans was 2.16(95%C.I.2.08-2.25) versus 1.85(95%C.I.1.75-1.95) in African Americans(p<0.0001), 2.16(95%C.I.2.08-2.24) in non-diabetics vs. 1.84(95%C.I.1.74-1.94) in diabetics(p<0.0001), and 2.22(95%C.I.2.13-2.32) in recipients <60 years vs. 1.83(95%C.I.1.74-1.92) in recipients ≥60 (p<0.0001). The relative hazard for diabetics at KDRI=0.5 was 1.49 but at KDRI=2.0 the hazard was significantly attenuated to 1.17; among African Americans the respective risks were 1.50 and 1.17 and among recipients over 60 1.64 and 1.22. Results indicate that the effects of donor risk are not uniform for transplant recipients with respect to overall graft loss. Donor quality has statistically and clinically significant interactions with recipient characteristics: the impact of donor risk varies dramatically with respect to recipient race, primary diagnoses, and age. Higher donor risk kidneys (e.g. high KDRI donor kidneys) have a diminished effect on older, diabetic and African American recipients relative to their counterparts whereas the effect of lower donor risk kidneys have a pronounced effect on graft survival between groups.

These findings are critical considerations for informed decision-making for transplant candidates.

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