Out-of-Sequence Lung Allocation and Outcomes for Bypassed Candidates in the United States.

Abstract

BACKGROUND Out-of-sequence (OOS) allocation allows organ procurement organizations (OPOs) to expedite organ placement outside of match-run order, but outcomes for candidates bypassed during OOS placement are poorly described. We evaluated the frequency, timing, and outcomes of candidates skipped when a lung offer was placed OOS. METHODS Using Scientific Registry of Transplant Recipients (SRTR) data, we identified all adult lung transplant prevalent candidates between 1/1/2021 and 11/30/2024. Candidates were classified as skipped if bypassed during an OOS offer. Competing-risk analyses estimated cumulative incidence of transplant, death, or removal for clinical deterioration following first skip. Cox models with time-dependent skip exposure evaluated associations with outcomes. Sensitivity analyses were restricted to candidates listed after implementation of Composite Allocation Score (CAS). RESULTS Among 12,967 candidates, 7,468 (58%) were skipped at least once. Median time from listing date (or 1/1/2021) to first skip was 9 days (IQR 3-26). After first skip, 6-month cumulative incidence was 74% for transplant, 2.0% for death, and 1.5% for removal due to deterioration. In time-dependent models, skipping was associated with a higher likelihood of transplant (adjusted HR 1.43, 95% CI 1.37-1.49) and lower hazard of death (adjusted HR 0.76, 95% CI 0.64-0.90). Center-level transplant rates among skipped candidates varied substantially, with a median of 218 (IQR 157-372) transplants per 100 patient years. CONCLUSION OOS allocation is common, occurs early after listing, and is not associated with worse short-term waitlist survival. However, marked center-level variation in post-skip transplant rates suggests heterogeneity in implementation and raises concern for inconsistent application of OOS practice and potential inequity in lung allocation.