Safety of blood group A2-to-O liver transplantation: an analysis of the United Network of Organ Sharing database.

Background: ABO-incompatible organ transplantation typically induces hyperacute rejection. A2-to-O liver transplantations have been successful. This study compared overall and graft survival in O recipients of A2 and O grafts based on Organ Procurement and Transplantation Network data.

Methods: Scientific Registry of Transplant Recipients data were used. The first A2-to-O liver transplantation was entered on March 11, 1990; all previous transplantations were excluded. Between March 11, 1990, and September 3, 2010, 43,335 O recipients underwent transplanation, of whom 358 received A2 grafts.

Results: There were no significant differences in age, sex, and race between the groups. Recipients of A2 grafts versus O grafts were significantly more likely to be hospitalized at transplantation (45% vs. 38%, P≤0.05) and to have a higher mean (SD) model for end-stage liver disease score (24 [11] vs. 22 [10], P≤0.05). 10% of A2 recipients and 9% of O recipients underwent retransplantation. No significant differences existed in rejection during the transplantation admission and at 12 months: 7% versus 6% and 20% versus 22% for A2 recipients and O recipients, respectively; and there were no significant differences in contributing factors to graft failure or cause of death. At 5 years, overall survival of A2 and O graft recipients was 77% and 74%, respectively (log rank=0.71). At 5 years, graft survival was 66% in both groups (log rank=0.52). Donor blood group was insignificant on Cox regression for overall and graft survival.

Conclusions: Using Organ Procurement and Transplantation Network/Scientific Registry of Transplant Recipients data, we present the largest series of A2-to-O liver transplantations and conclude this mismatch option to be safe with similar overall and graft survival. This opens possibilities to further meet the demands of a shrinking organ supply, especially with regard to expanding living-donor options.