Association between recipient blood type and heart transplantation outcomes in the United States

BACKGROUND: In heart transplantation (HT), although blood type O organs can go to any blood type, non-O organs may not be allocated to adult O recipients. Therefore, O candidates wait longer than non-O candidates and frequently require bridging with left ventricular assist devices (LVADs). The effects of this discrepancy are rarely investigated in a large registry. The purpose of this study was to assess the association between candidates’ blood type and their outcomes after HT listing. METHODS: This is a retrospective cohort study using the United Network for Organ Sharing Registry, including 34,352 candidates listed for a single-organ, primary HT from January 2000 through December 2015. Main outcome measures were waitlist mortality and post-HT mortality, using blood type A as reference. We conducted inverse-probability weighting to adjust for baseline profiles. RESULTS: Among 34,352 candidates (median age 55, interquartile range 46–62; female 24.8%; blood type A: 13,258, AB: 1,572, B: 4,599, O:14,923), 22,714 candidates (A: 71.5%, AB: 82.1%, B: 73.0%, O: 57.5%; p < 0.001) underwent HT during the study period. Among recipients, bridging LVAD rate was highest in O recipients (A: 23.0%, AB: 15.3%, B: 23.4%, O: 32.1%; p < 0.001). After inverse-probability weighting, O patients demonstrated a significantly higher hazard of death after listing (adjusted hazard ratio 1.11, 95% confidence interval [CI] 1.07–1.16) and after HT (adjusted hazard ratio 1.07, 95% CI 1.01–1.13) as compared with A. CONCLUSIONS: There is a survival discrepancy among blood types. Our findings should facilitate more prospective studies to revisit current policies regarding equity in allocation, where possible.