Blood Donor RBC Genotyping at the National Advisory Unit on Immunohematology at Oslo University Hospital

<b>Background:</b> Blood transfusion has an essential place in the treatment of several patient groups but entails alloimmunization risk. The provision of phenotype-matched packed red blood cell concentrates (PRBCCs) is recommended for preventing alloimmunization in lifetime transfusion-dependent patients, while antigen-negative PRBCCs are a prerequisite for patients that already have blood group antibodies against clinically significant antigens. A large blood donor corps that is extendedly typed for clinically important red blood cell (RBC) antigens is therefore extremely valuable and can be achieved by high-throughput RBC genotyping. Probability of finding antigen-negative PRBCCs will then increase. <b>Methods:</b> RBC genotyping was performed using EDTA-blood. Following DNA extraction, ID CORE XT, a multiplex PCR- and hybridization-based genotype test utilizing Luminex xMAP technology, was employed. The predicted phenotypes were reported. <b>Results:</b> In this retrospective study, 92,796 RBC antigens were genotyped in 2508 blood donors, analyzing 48 donor samples in one setup, between 2015 and 2021. These results were compared with results available from serologic phenotyping, and discrepancies were investigated. Antigen-negative blood donors, especially those negative for clinically significant high-frequency antigens, combinations of antigen-negatives and positives for low-frequency antigens, were identified, in addition to variants. <b>Conclusions:</b> In the vast majority of discrepancies, repeat serology confirmed the genotype result. Therefore, we conclude that RBC genotyping using ID CORE XT is an effective and accurate method that complements serology. As many donors stop donating blood due to various reasons, we must continue genotyping to maintain and preferably increase the number of extendedly typed blood donors, which are needed for the provision of antigen-negative blood units.