Platelet donor selection for HLA-immunised patients; the impact of donor-specific HLA antibody levels.

Background: Approximately 20% of patients with a recurrently poor platelet transfusion increment show human leukocyte antigen (HLA) alloantibodies. The aim of this study was to analyse the impact of mean fluorescence intensity (MFI) levels of donor-specific HLA antibodies and the feasibility of the HLAMatchmaker algorithm in donor selection.

Study Design And Methods: A total of 270 HLA-typed platelet transfusion responses of 40 patients were included in the study. The patients' immunisation status was determined with Luminex-based methods, and HLA alloantibody strengths were defined as the MFI. For the Matchmaker eplet matching, the HLA-ABC Eplet Matching Version 2.1 was used.

Results: In 62% of the 270 transfusions, HLA antibodies against the transfused platelets were present, with a median cumulative MFI level of 2026 (range: 299-29 203). In multivariate analysis, a cumulative MFI level higher than 1000 emerged as an independent risk factor for a poor platelet transfusion increment, along with infection and the age of the product.

Conclusion: The HLAMatchmaker algorithm alone is not a sufficient tool for donor selection. Donor selection based primarily on the levels of donor-specific HLA antibodies is a preferable practice.