ABO-Nonidentical Transfusions Linked to Lower Survival in Massive Transfusion Patients

Trauma patients who received five or more ABO-nonidentical blood components during massive transfusion had a higher mortality risk than those who received fewer, according to a single-center study published as a research letter in JAMA Surgery. According to the authors, determining a patient's ABO type as soon as feasible and providing ABO-identical components as a policy might improve outcomes in some cases.

Researchers at the University of Rochester Medical Center analyzed 403 patients who required activation of the massive transfusion protocol at the center's level 1 trauma center between 2008 and 2020. The center's practice was to switch to ABO-identical red blood cells as soon as feasible after the initial group O shipment and to use ABO-identical platelets, plasma and cryoprecipitate when possible. The study period predates the center's adoption of group A plasma and low-titer group O whole blood.

Among the 42 patients who received five or more ABO-nonidentical components, mostly red blood cells, 48% survived 24 hours and 31% survived to hospital discharge. Both rates were significantly lower than among patients who received four or fewer ABO-nonidentical components. Receiving one to four nonidentical components was not associated with worse survival. Among patients given six to 15 total components, the authors reported that mortality was approximately twice as high with ABO-mismatched components.

Overall survival did not differ by patient ABO group. Among 24-hour survivors, however, hospital mortality was 30% among patients whose cells carried the A antigen, compared with 18% among those without it. The authors said they could not determine whether this reflected a biologic effect or confounding.

The authors noted several limitations. The study was retrospective and conducted at a single center, with unadjusted comparisons and no correction for multiple comparisons. Because of its observational design, the study cannot establish a causal relationship between ABO-nonidentical transfusions and mortality.

Lead author Neil Blumberg, MD, said he believes the findings are consistent with a causal relationship. He pointed to previous observational studies reporting associations between ABO-mismatched transfusions and mortality, as well as laboratory evidence suggesting that ABO-mismatched transfusions may impair platelet and endothelial cell function and increase inflammation. He also cited a 2011 report from the University of Rochester in which mortality among surgical patients decreased after the institution stopped using ABO-nonidentical transfusions.

The authors also noted that few transfusion services prioritize ABO-identical platelets and cryoprecipitate as their center did, which may make the results difficult to confirm elsewhere. They concluded that future studies of transfusion resuscitation should consider patient ABO type and receipt of ABO-nonidentical transfusions when assessing efficacy and safety.

In a University of Rochester news release, Blumberg emphasized that transfusions are often lifesaving and that, in trauma, their benefits may outweigh concerns about ABO mismatch. He said the findings point to a need to develop a universal donor product, group O blood with A and B antibodies reduced or removed, although current methods are not widely available or practical.