Recipient Selection and Outcomes After Out-of-Sequence Kidney Allocation Since Implementation of Kidney Allocation System 250 (KAS250): A Single-Center Experience.

INTRODUCTION: Allocation out of sequence (AOOS) of kidneys has increased after KAS250 and raised concerns regarding transparency and equitable recipient selection. Less is known about recipient selection and outcomes at individual centers. METHODS: We performed a single-center retrospective study of adult deceased donor kidney transplants at the University of Wisconsin from March 15, 2021, to March 31, 2024. Recipients receiving kidneys classified as AOOS were compared with contemporaneous recipients of non-AOOS kidneys. Donor and recipient characteristics, delayed graft function, graft function, and patient and graft survival were assessed. Standardized data explaining why kidneys entered AOOS allocation were unavailable. RESULTS: Among 498 deceased donor kidney transplant recipients, 89 (17.9%) received AOOS classified kidneys. Donor characteristics were largely similar, although kidneys categorized as AOOS had higher terminal creatinine (1.6 vs. 1.2 mg/dl, p = 0.03) and longer cold ischemia time (22.9 vs. 20.4 h, p = 0.003). AOOS recipients were older, more often preemptive, had shorter waiting times, and were less likely to be retransplant recipients or have cPRA > 20%. Recipient sex and race did not differ. Four-year adjusted patient survival (aHR 0.85; 95% CI 0.38-1.94; p = 0.71) and graft survival (aHR 0.72; 95% CI 0.34-1.54; p = 0.40) were not statistically different. CONCLUSION: In this single-center experience, transplantation of kidneys categorized as AOOS was associated with distinct recipient selection, comparable 4-year outcomes, and without compromising gender/racial balance.