Background and objectives: Weak ABO variants may escape tests using unlicensed sera.
Materials and methods: Prior to transfusion, ABO grouping was performed using an automated system and in-house diluted sera, and manual and bedside test techniques. Genotyping and sequencing were performed using standard methods.
Results: Initially, the red blood cells (RBC) of the first-time blood donor were typed as B, but pretransfusion testing carried out using the bedside test indicated the presence of an additional A phenotype. Serological re-examination confirmed the bedside test results, and the allele in question was identified, by genotyping, as a new weak A variant (Aw11).
Conclusions: The use of CE-marked and licensed antisera is recommended to avoid ABO mistyping.