Human leukocyte antigen sensitization from red cell transfusions: Rate and risk factors in renal and nonrenal patients requiring transfusion.

De novo blood donor-specific human leukocyte antigen (HLA) antibodies (bDSA) from red cell transfusions can complicate solid organ transplantation, but the incidence rate is uncertain. We conducted a prospective observational study to assess the cumulative incidence rate of de novo bDSA in a cohort of patients with chronic kidney disease and no prior transplant, patients with prior kidney transplants (with or without continuing immunosuppression), and a general patient population. HLA antibody testing was performed before and 6 to 8 weeks after transfusion, with patient and blood donor typing. De novo HLA class 1 bDSA were detected in 10.8% (12 of 111) participants at a "weak" cutoff and in 7.2% (8 of 111) at a "moderate/strong" cutoff. De novo HLA class 2 bDSA were detected in 0.9% (1 of 111) at both cutoffs. Risk factors identified for HLA class 1 de novo bDSA included female sex (P < .001) and pretransfusion HLA antibodies (P = .02). The posttransplant group had low de novo bDSA (1 of 37, 2.7%). Additional testing suggested anamnestic (rather than de novo) responses in some participants. Red cell transfusions are associated with de novo bDSA, especially to HLA class 1 antigens, and measures to prevent sensitization, including selecting donors to avoid mismatches, may be warranted for some groups.