Listing for blood type A2 donors is highly variable and impacts waitlist outcomes among blood type O liver transplantation candidates in the United States.

Abstract

Blood type O liver transplantation (LT) candidates in the United States face the highest waitlist mortality due to the broader compatibility of type O grafts. Although blood-type compatible transplant is a gold standard, type O candidates might benefit from listing for A2 donors, whose antigen is known for its decreased immunogenicity. This study examines the trends and impact on waitlist outcomes of listing for A2 donors among 67,756 type O LT candidates listed between 2010 and 2023 using data from the United Network for Organ Sharing database. The number of A2-to-O LTs increased steadily, with 117 LTs performed in 2023. 61.1% of type O candidates were listed for A2 donors, with considerable regional variations. Fine-Gray competing risk analysis revealed that listing for A2 donors was associated with reduced waitlist dropout rates (subdistribution hazard: 0.94, P < 0.001) and increased transplant probabilities (subdistribution hazard: 1.07, P < 0.001), especially in regions with longer wait times, among candidates with listing Model for End-Stage Liver Disease (MELD)-Na scores between 15 and 34, and candidates listed after the Acuity Circles policy implementation. These findings suggest listing for A2 donors should be encouraged to improve waitlist outcomes for type O candidates.