Identification of specificities of antibodies against human leukocyte antigens in blood donors

BACKGROUND: Transfusion‐related acute lung injury (TRALI) is the leading cause of transfusion‐related mortality. Blood centers are implementing TRALI risk reduction strategies based on screening apheresis donors for antibodies to human leukocyte antigens (HLA). STUDY DESIGN AND METHODS: HLA antibody screening was performed on 7920 blood donors from the Leukocyte Antibody Prevalence Study (LAPS) using Luminex‐based normalized background (NBG) cutoff ratios of 10.8 (Class I) and 6.9 (Class II). Single antigen bead (SAB) assay cutoffs of 2500 median fluorescence intensity units (Class I) and 1500 (Class II) were established based on results of two subpopulations of LAPS donors. Antibody frequencies against HLA A, B, C, DR, DQ, and DP antigens were determined for screen‐reactive donors with prior pregnancies. RESULTS: SAB reactivity for samples above our multiantigen bead NBG cutoffs was 78% for Class I and 79% for Class II. The SAB‐positive rate increased among women with zero to four or more pregnancies (0.3%‐15.6% Class I and 0.4%‐18% Class II; p