Background: Difficulties in the demonstration of expected isoagglutinins is a common problem in ABO reverse typing. Some nondeletional ABO*O alleles have been shown to encode for the expression of minimal amounts of A antigen, resulting in very weak anti-A activity in some cases. It is unknown whether minor problems with ABO reverse typing are related to specific ABO*O alleles.
Study design and methods: Among 2196 blood group O red cell (RBC) donations, the ABO alleles of those donations in which the isoagglutinins were incorrectly identified were analyzed with an autoanalyzer. The presence of nondeletional ABO alleles was determined by sequence-specific priming and sequencing.
Results: Fifty (2.3%) of the group O RBC donations tested had to be typed manually because of isoagglutinin detection problems in automated typing: reduced anti-A activity was observed in 45 cases, reduced anti-B activity in 4 cases, and variably reduced isoagglutinin activity in 1 case. The nondeletional ABO*O alleles ABO*O03 and ABO*Aw08 were implicated in 38 of these 50 cases (1.7% of all blood group O donors). The remaining samples, including those with reduced anti-B activities, were homozygous for deletional ABO*O alleles.
Conclusion: Nondeletional ABO*O alleles are the most frequent cause of isoagglutinin detection problems in blood group O donors.