Wednesday, August 10, 2022
HomeAmerican Journal of Transplantationindex/list_12275_1Hardest-to-Place Kidney Transplant Outcomes in the United States

Hardest-to-Place Kidney Transplant Outcomes in the United States

Abstract and Introduction


The outcomes of hardest-to-place kidney transplants—accepted last in the entire match run after being refused by previous centers—are unclear, potentially translating to risk aversion and unnecessary organ discard. We aimed to determine the outcomes of hardest-to-place kidney transplants and whether the organ acceptance position on the match run sufficiently captures the risk. This is a cohort study of the United Network for Organ Sharing data of all adult kidney-only transplant recipients from deceased donors between 2007 and 2018. Multiple regression models assessed delayed graft function, graft survival, and patient survival stratified by share type: local versus shared kidney acceptance position scaled by tertile. Among 127 028 kidney transplant recipients, 92 855 received local kidneys. The remaining received shared kidneys at sequence number 1–4 (n = 12 322), 5–164 (n = 10 485) and >164 (n = 11 366). Hardest-to-place kidneys, defined as the latest acceptance group in the match-run, were associated with delayed graft function (adjusted odds ratio 1.83, 95% confidence interval [CI] 1.74–1.92) and all-cause allograft failure (adjusted hazard ratio [aHR] 1.11, 95% CI 1.04–1.17). Results of this IRB-approved study were robust to the exclusion of operational allocation bypass and mandatory shares. The hardest-to-place kidneys accepted later in the match run were associated with higher graft failure and delayed graft function.


A kidney transplant improves quality and quantity of life at reduced costs compared with dialysis,[1,2] yet only 20% of waitlisted individuals are transplanted each year in the United States (US).[3] Concurrently, 20% of all kidneys recovered for transplantation are discarded every year,[4–6] a proportion high above that of the United Kingdom (10%–12%)[7,8] and France (9.1%).[9] Kidney discard in the US is largely related to uncertainty about kidney quality and risk aversion by transplant programs.[6,10–13] There is no precise measure of kidney quality, so it is unclear which discarded kidneys would have similar outcomes to accepted kidneys with similar characteristics. Exacerbating uncertainty about donor quality is regulatory scrutiny. Each US transplant program’s results are publicly reported every 6 months by the Scientific Registry of Transplant Recipients (SRTR), showing observed and expected outcomes derived from risk-adjusted models.[14] While the risk-adjusted models evaluating transplant program outcomes are statistically valid,[14] there are concerns that these models fail to capture important donor factors that influence patient outcomes.[15] Accepting an organ with characteristics that are inherently risky but are not captured in risk adjustment places the program at risk of being rated as underperforming.[14]

Although the outcomes of discarded kidneys cannot be assessed, the outcomes of hardest-to-place kidneys that are declined by the majority of transplant centers before being ultimately accepted may provide useful information. The current outcomes of hardest-to-place kidneys are unclear because previous studies analyzed historic cohorts (spanning 2000–2013)[16–18] and chose low organ refusal thresholds at positions 9[17] and 50,[16] thereby not measuring truly hardest-to-place kidneys. As many as one-fourth of transplanted kidneys are refused at least 75 times before eventually being transplanted due to low quality.[19]

To examine outcomes of hardest-to-place kidneys at extreme positions of kidney turndown, we used United Network for Organ Sharing (UNOS) match-run and recipient data to quantify the association of position of kidney acceptance and graft failure, mortality, and delayed graft function, accounting for recipient and donor characteristics. Additionally, we explored whether the organ acceptance position on the match run sufficiently captures the risk. We hypothesize that hardest-to-place kidneys have worse post-transplant outcomes even with risk adjustment by other factors typically ascertained within the SRTR database.

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