The use of a potential novel tool in virtual crossmatching for platelet transfusion in platelet refractoriness.

Background And Objectives: Transfusion support for immune-mediated platelet refractoriness (PR) is clinically challenging, technically laborious and costly. The development of 'EpHLA/EpVix software' has been used successfully to select kidney donors. Here, we sought to evaluate this new software as a tool for platelet virtual crossmatch (VxM).

Materials And Methods: This is a prospective study from 2007 to 2014 of PR patients in a tertiary hospital. Platelet components selected by HLAMatchmaker program were crossmatched by EpHLA/EpVix, anti-human globulin complement-dependent lymphocytotoxicity test (AHG-CDC), flow cytometry platelet crossmatch (FCxM) and then compared. Effectiveness of platelet components transfused was evaluated by CCI.

Results: Ninety-seven crossmatched platelet transfusions for 27 patients were enrolled. Partial matches were analysed for 75 transfusions by the 3 methods, and 22% showed discrepant results among the assays. After further analysis, data showed that all divergent cases could be explained by HPA alloimmunization, prozone effect (FCxM), low sensitivity of AHG-CDC and possible interference in FCxM/AHG-CDC assays. Notably, sensitivity and specificity of VxM analysis was excellent (100%). Satisfactory CCI counts were obtained for the majority (22/30) of the transfusions.

Conclusion: The new EpHLA/EpVix method showed to be effective, feasible and fast for VxM at no cost and able to minimize labour on donor identification. However, platelet crossmatching may be a necessary step because EpHLA/EpVix does not formally exclude HPA alloimmunization.