Influence of U.S. lung composite allocation score components on transplant candidate prioritization

Since implementation of the Composite Allocation Score (CAS) in March 2023, exception requests have increased, suggesting potential misalignment between policy intent and the actual prioritization achieved. Using the Scientific Registry of Transplant Recipients, we computed CAS component scores and quantified each component's contribution to total CAS variability. Medical urgency constitutes 25 of the 100 possible CAS points but was responsible for 40.6% of variation in total scores. Biological disadvantage is assigned 15 points but accounted for 33.3% of CAS variation; and geographic efficiency is assigned 10 points but drove 16.6% of variation. Posttransplant survival (25 points) accounted for the most points received but explained only 6.4% of variation. These results indicate that lung transplant candidate prioritization in the United States is dominated by medical urgency, biological disadvantage, and geographic efficiency, revealing a divergence between intended and actual contributions of CAS components to total scores.