Routine Solid Phase Multiplex Anti-HLA Antibody Tests Predict Platelet Refractoriness

Objectives: No validated screening methods identify patients at risk for human leukocyte antigen (HLA) alloimmune-mediated platelet refractoriness (alloPR). We determined if bead-based HLA antibody tests could predict risk of developing HLA alloPR. Methods: Hematopoietic progenitor cell transplant patients screened for HLA antibodies without prior refractoriness were identified. Phenotype bead screening results were compared between patients who later did and did not develop alloPR. Results: Seven of 27 patients identified subsequently developed alloPR. The panel reactive antibody (PRA) and mean fluorescence intensity (MFI) of the 10 most reactive beads in the initial screen were significantly higher among patients who later developed alloPR (P < .001). Specifically, PRA of more than 30% and mean MFI of 1,500 or more in the most reactive beads identified at-risk patients. Administration of HLA-compatible platelets yielded significant posttransfusion count increments compared with routine platelets. Conclusions: HLA antibody screening by phenotype bead assay may prospectively identify at-risk patients for the development of alloPR. However, clinical trials are needed to validate these findings.