Haemolytic transfusion reactions caused by non‐ABO red cell antibodies reported to the Norwegian Haemovigilance System 2004–2020.

Background and Objectives: The aim of this study was to analyse the reports received in the Norwegian Haemovigilance System from 2004 to 2020 on acute and delayed haemolytic transfusion reactions caused by non‐ABO red cell antibodies. Materials and Methods: Antibody specificity, clinical symptoms and outcomes were included when available. Results: After transfusion of 3.7 million red cell concentrates, reports on 78 cases of haemolytic transfusion reactions caused by non‐ABO red cell antibodies were received, corresponding to an incidence of 1 in 47,000 transfused red cell concentrates. There were 30 acute and 48 delayed haemolytic transfusion reactions. A total of 113 red cell antibodies were found: 82 alloantibodies, 6 autoantibodies and 25 cases where the antibody specificity could not be determined. Two fatalities occurred: one caused by anti‐Wra and one caused by an unidentified red cell antibody. The most frequently reported antibody specificities were those in the Rh and Kidd blood group systems, representing 24% and 14%, respectively, of all the antibodies identified. In six cases, errors occurred, leading to the issuing of blood units without the required phenotype match. Conclusions: Despite the possible underreporting, the low number of serious haemolytic transfusion reactions reflects an adequate pre‐transfusion practice by the Norwegian blood banks. [ABSTRACT FROM AUTHOR]