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Published on: February 14, 2022
Geography as a Determinant of Donor Access for Lung Transplantation in the United States
Maryam Valapour1, Paul R Gunsalus2, Johnie Rose3
1Departments of Pulmonary Medicine, Cleveland Clinic, Cleveland, OH.
Background:
Geographic equity in access to donor lungs is a central objective of US organ allocation policy. In March 2023, lung allocation transitioned from rigid donor-candidate distance thresholds to a continuous distribution framework using the Composite Allocation Score (CAS). The CAS prioritizes medical urgency, projected posttransplant survival, biological compatibility, and geographic efficiency (continuous donor-candidate distance). On May 7, 2026, a policy amendment was implemented that increased the influence of proximity on candidate ranking.
Research Question:
Is listing transplant center location associated with effective donor availability, and how will the amended CAS policy affect candidate prioritization?
Study Design And Methods:
We conducted a retrospective cohort study using Scientific Registry of Transplant Recipients data including adult lung transplant candidates, recipients, and donors (September 27, 2023-December 1, 2024). The primary outcome was distance-adjusted donor availability, defined as biologically compatible donors recovered within 30 days of listing, weighted by the CAS geographic efficiency function. Spatial regression evaluated geographic variation across transplant centers. Counterfactual analyses investigated allocation under the CAS amendment. Match-run analyses assessed changes in candidate prioritization for donor organs recovered during the study period.
Results:
Among 3,917 candidates from 61 centers, median center-level distance-adjusted donor availability was 1.90 donors per candidate-day (interquartile range, 1.75-2.14), with substantial variation across centers and regions. After adjustment for center size and candidate biological characteristics, location remained significantly associated with donor availability. The amended policy would reduce effective donor availability and increase geographic disparities in donor access. In match-run analyses, 23.9% of candidates ranked within the top 10 under the prior CAS policy fell outside the top 10 under the amended CAS policy. Candidates with biological barriers to donor matching, including blood type O, experienced greater deprioritization.
Interpretation:
Our results show that geographic variation in effective donor availability persists under CAS policies. Increasing the influence of donor-candidate proximity may increase geographic disparities in donor access, particularly for harder-to-match candidates.
