AABB2025: Should Transfusion Services Accept RBC Units Containing Unexpected Donor Alloantibodies?

With an aging donor population and inventories often under pressure, the blood community continues to look for new ways to make efficient use of every available red blood cell (RBC) unit.

One approach highlighted at Saturday’s oral abstract session, “Lessons From the Immunohematology Lab,” was the use of units containing unexpected donor alloantibodies (CUDA). These alloantibodies are extremely rare, but when present, the units are often discarded due to transfusion safety concerns.

In her abstract presentation, Natasha Leon, MLS(ASCP)SBB, shared evidence supporting the safe use of such RBC units. The study, led by investigators from Versiti and the Medical College of Wisconsin, explored the safety of transfusing antibody-positive RBCs and highlighted the potential to promote more efficient stewardship of the blood supply.

In the single-center study, Leon and her coinvestigators analyzed retrospective data from 34 CUDA RBC units transfused to 26 recipients. Fifteen of the 34 units underwent antibody titration, which showed a one- to three-dilution reduction in antibody strength between donor samples and the final RBC product. Investigators found no evidence of hemolytic transfusion reactions or other adverse events within 72 hours post-transfusion, and serologic review showed no new antibody development attributable to transfusion. One patient demonstrated a new positive direct antiglobulin test consistent with a preexisting warm autoantibody.

Overall, the findings suggest that RBC units containing donor alloantibodies can be safely transfused without increasing laboratory workload. The study also highlighted the potential to preserve valuable inventory, as 22 of the 34 units — most of them group O — may  otherwise have been discarded.

These findings support the potential for broader acceptance of antibody-positive RBC units, helping transfusion services use scarce blood resources more efficiently without compromising patient safety.