No increase in anti-A isohemagglutinin titer after SARS-CoV-2 infection: A retrospective cohort analysis of group O apheresis platelet donors.

The risk of a hemolytic reaction during the transfusion of ABO non-identical PC is determined by the presence of natural anti-A IgM antibodies, the titer of which may increase after infections. The aim of the study was to evaluate the titer of anti-A isohemagglutinins in platelet concentrate (PC) obtained by apheresis from group O donors who experienced SARS-CoV-2 infection, and to compare the titer before and after infection. A retrospective single-center analysis of 21 PC donors with a previous COVID-19 history was performed. The results showed neither a statistically important increase in the anti-A IgM antibody titers nor a significant correlation between the anti-A IgM antibody level and anti-SARS-CoV-2S1 antibody titer in the donors with an asymptomatic or mild COVID-19. Further population-based studies on anti-A titers are necessary for a comprehensive assessment of this phenomenon.