Association Between Allocation Out-of-Sequence and Organ Nonuse in Contemporary Lung Transplantation: An Analysis of the UNOS National Registry.

Abstract

Allocation out-of-sequence (AOOS) is an allocation pathway that allows organ procurement organizations (OPOs) to bypass the standard match-run sequence to expedite organ placement and avoid organ wastage amidst donor, recipient, or logistical constraints. Amidst increasing use of AOOS in recent years, we sought to characterize its impact on lung utilization in the contemporary era. We performed a retrospective analysis using United Network for Organ Sharing data from June 2021 to December 2024 to examine the association between OPO-level AOOS and lung nonuse. Among 10,350 lung donors, 931 (9.0%) were allocated out-of-sequence, with OPO-level rates of AOOS ranging from 1.2% to 28.9%. Observed-to-expected lung yield ratios were comparable across OPOs stratified by AOOS use, with no significant difference among low-, medium-, and high-AOOS groups (0.96 vs 0.97 vs 0.92; p=0.728). Among 20,462 individual lungs recovered for transplantation, 2,003 (9.8%) ultimately not used. After adjusting for donor characteristics and temporal trends, AOOS was not significantly associated with lung nonuse (incidence rate ratio 1.00, 95% confidence interval 0.94-1.06, p=0.883). These findings indicate that further revision of lung allocation policy is required to optimize lung utilization and mitigate use of alternative allocation pathways.