Identification of rare blood group donors from biobank data.

Safe blood transfusion relies on avoiding clinically significant incompatibilities between recipient antibodies and donor red blood cell antigens, a requirement that becomes particularly challenging for patients with rare blood group phenotypes, especially when alloimmunized. Conventional approaches to identifying rare blood group donors rely on targeted screening and laborious laboratory studies, which are limited by resource constraints and insufficient population diversity. The aim of this study was to enhance the identification of rare blood group donors in Finland by utilizing genome-wide data from our national Blood Service Biobank. Genomic variants associated with rare phenotypes were screened in 56 997 blood donors, after which the rare blood group was confirmed using routine methods. To estimate the need for rare blood group units, we utilized data from the Helsinki University Hospital (HUS) Data Lake and the laboratory information system of the HUS Blood Bank. Eighty-six new rare donors were identified, with complete concordance between genomic results and confirmed phenotypes. Patient data highlighted donor needs and identified rare phenotypes, particularly those more prevalent among individuals of African ancestry. These findings demonstrate the value of biobank genomic data in expanding rare donor registries and improving transfusion preparedness.