Seasonal variability is not observed in the rates of high anti-A and anti-B titers in plasma, apheresis platelet, and whole blood units tested by different methods.

The prevalence of high-titer plasma, AP, and WB units varies by titer method and local definition of high titer. Even at the lowest titer threshold of 50, a significant proportion of units had a high-titer antibody, although the clinical relevance of this finding needs further investigation.