Outcomes of Deceased Donor Kidney Transplants Allocated Out of Sequence in the United States

Background: Changes in kidney allocation policies and regulations of organ procurement organizations have impacted the volume of organ offers and challenged transplant providers. One consequence is increased kidneys allocated out of sequence (OOS). Methods: Retrospective observational study using Scientific Registry of Transplant Recipient data from 2021-2023, we analyzed donor and recipient characteristics for OOS vs. standard kidney allocation and multivariable Cox models to evaluate graft survival. We also compared paired donors (one kidney OOS and the other standard allocation). Results: Annual OOS kidney allocation rates increased from 5.4% in 2021 to 18.4% in 2023. High OOS-use centers increased from 5 (2.2%) between 2021 and June 2022 to 37 (17%) in 2023. Listing at a high-OOS usage center was associated with increased rate of deceased donor transplantation [Adjusted Hazard Ratio [AHR]=3.07, 95% CI (2.90,3.25)]. Recipients of OOS allocation were more likely to be male (66 vs. 59%), White race (38 vs. 32%), privately insured (29 v. 24%), and preemptively transplanted (18 vs. 10%). Overall graft loss was not significantly different between OOS and standard allocated transplants [AHR=0.94, 95%CI (0.85, 1.05)], consistent in paired donor analysis [AHR=1.10, 95%CI (0.86, 1.41)]. Conclusion: Short-term kidney graft failure does not differ between OOS and standard allocation. High-OOS kidney centers have higher deceased donor transplant rates. Further investigation is needed to understand demographic differences and factors explaining OOS allocation.