Out-of-sequence lung allocation and outcomes for bypassed candidates in the United States

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.

Using Scientific Registry of Transplant Recipients (SRTR) data, we identified all adult lung transplant prevalent candidates between January 1, 2021 and November 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).

Among 12,967 candidates, 7468 (58%) were skipped at least once. Median time from listing date (or January 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.

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.