The impact of increasing out-of-sequence allocation on kidney transplant patient outcomes

The use of allocation out of sequence (AOOS) of donor kidneys has increased in recent years in the US. The impact on candidate and recipient outcomes is unknown. Using data from the Scientific Registry of Transplant Recipients, we analyzed 83 811 adult candidates who were listed for a single-kidney transplant between January 1, 2022, and December 31, 2023, to compare waitlist outcomes between candidates listed at centers with varying out-of-sequence use. We also investigated the impact on posttransplant all-cause graft failure using an analysis of 37 266 adult single-kidney transplant recipients who received a transplant from January 1, 2022, to December 31, 2023. Compared with candidates listed at centers that did not accept any offers via AOOS in the 6 months prior to listing, candidates at centers that accepted 10%, 20%, and 30% of offers via AOOS had 4% (hazard ratio [HR]: 1.04, 95% CI: 0.97-1.11), 27% (HR: 1.27, 95% CI: 1.17-1.37), and 81% (HR: 1.81, 95% CI: 1.60-2.04) increases in rates of deceased donor transplant. All-cause graft failure by out-of-sequence vs standard allocation did not differ in analysis adjusted for recipient and donor characteristics (HR: 1.03, 95% CI: 0.93-1.15), suggesting a greater impact for pretransplant outcomes. System-wide variation in the use of AOOS has contributed to differential access to kidney transplants.