An in silico simulation of the frequency of administering HLA-incompatible low titer group O whole blood units when the donor pool includes unscreened female donors.

Background: As low titer group O whole blood (LTOWB) increases in popularity, blood centers are finding innovative ways of maintaining the supply. One potential way is collecting LTOWB from parous female donors without testing for HLA antibodies. This in silico simulation predicted the risk of an LTOWB unit containing an HLA antibody and the subsequent risk for an HLA-incompatible transfusion.

Methods: An LTOWB blood bank with 1 million units was simulated consisting of male, nulliparous, and parous female donors. The proportion of each donor type was modeled after the sex distribution at US blood centers. The parity of female donors was calculated based on the average number of live births per female depending on her age. HLA-alloimmunization risk was determined by her parity status. The HLA haplotypes of the simulated recipients were derived from the 100 most common HLA haplotypes in the US National Marrow Registry Program database. The proportion of different race/ethnic groups in the US was used to simulate 100,000 LTOWB recipients to whom between 1 and 10 units were administered.

Results: Overall, the risk of an LTOWB unit containing at least one HLA antibody was 12.2% and the rate of receiving an HLA-incompatible unit was 21.3%. The risk of receiving an HLA-incompatible unit rose from 4.8% after receipt of one unit to 36.5% after 10 units.

Conclusion: Blood collectors and hospitals should evaluate the potential TRALI risk against the benefit of a potentially expanded inventory of LTOWB before collecting plasma-containing products from non-HLA-tested parous female donors.