Liver transplantation disparties by ABO blood type in the machine perfusion era

Introduction: United States Organ Procurement and Transplantation Network (OPTN) liver allocation policy prioritizes ABO-identical donor-recipient matching. However, ABO-nonidentical liver transplants are permitted to ensure access to transplantation for blood type AB candidates, given that only 3% of deceased liver donors are blood type AB. This policy has historically allowed blood type AB liver transplant candidates to be transplanted at higher rates than candidates with other ABO blood types, given their broader pool of ABO-compatible donors. Whether this disparity in access to liver transplantation persists in the normothermic machine perfusion (NMP) era, where the ability to safely extend preservation times has enabled broader geographic sharing of liver grafts, remains unexplored.
Methods: We used United Network for Organ Sharing (UNOS) data to examine trends in the person-time rate of adult deceased-donor liver transplantation by ABO blood type from 2012 to 2025. We then compared the demographic and clinical characteristics of liver recipients and donors stratified by recipient ABO blood type for the NMP era: January 1, 2022 to December 31, 2025.
Results: From 2012 to 2025, the rate of transplantation in blood type AB candidates consistently exceeded that of candidates with other ABO blood types, and this disparity widened in the NMP era. Blood type AB candidates were more likely to receive ABO-nonidentical grafts (45.5% versus 3.2 – 24.2% for other ABO blood types, p < 0.001) as well as grafts transported over longer distances than candidates with other ABO blood types (median [interquartile range] distance from donor hospital to transplant center in nautical miles: AB 217 [82 – 392], A 142 [50 – 305], B 147 [52 – 309], O 133 [39 – 300], p < 0.001) and were transplanted at lower MELD scores (median MELD at transplant [interquartile range]: AB 27 [17 – 31], A 27 [20 – 34], B 25 [18 – 32], O 27 [20 – 34], p < 0.001). Furthermore, blood type AB candidates received livers from younger donors (median [interquartile range] donor age in years: AB 41 [30 – 53], A 45 [33 – 58], B 44 [32 – 56], O 46 [34 – 58], p < 0.001) who were less likely to be donors after circulatory death (14.8% donor after circulatory death versus 21.1 – 28.0% for other ABO blood types, p < 0.001).
Conclusion: Disparities in liver transplantation rates by recipient ABO blood type have increased in the NMP era. NMP has enabled longer preservation times, functionally expanding the donor pool that was previously constrained by the imperative to minimize cold ischemia time and facilitating broader geographic sharing of liver grafts. These findings have important implications for liver allocation policy as NMP continues to reshape the geographic and logistical barriers to transplantation.