Platelet component transfusion and alloimmunization: Where do we stand?

Platelet transfusion in patients, particularly in onco-haematology, is frequent and can become chronic in some cases. Post-transfusion alloimmunization is often seen, in practice. The risk of this is significantly improved in multitransfused patients. Several classes of antigens binding on platelets (HLA and HPA) are involved and also red blood cell antigens (residual red blood cells in platelet concentrates). Platelet alloimmunization causes a poor transfusion response, refractoriness and, more rarely, post-transfusion purpura. In an alloimmunized recipient, the efficiency of platelet transfusion is based on the selection of compatible products. Significant technical progress means that several methods are currently available to ensure a good post-transfusion platelet count and a satisfactory clinical outcome for the patient.