Less than 1 percent of residents tested had positive antibody screens. Anti-E and anti-Le(a) were more common than anti-K. Wr(a) and C(w) were more potent antigens than K. Most antibodies showed an increase in frequency with increasing age. Except for anti-C and -D and anti-Le(a) and -Le(b), RBC alloantibodies did not occur in clusters.

Recently, a trend toward a decrease in the incidence of DHTR and a significant increase in DSTRs has occurred at the Mayo Clinic. These changes are most likely due to a combination of factors, including a decrease in average LOS and the adoption of the polyethylene glycol antibody detection system.