Recognition and management of antibodies to human platelet antigens in platelet transfusion–refractory patients

Platelet transfusion refractoriness is a problem for parous and multiply transfused patients, placing them at higher risk for morbidity and mortality when posttransfusion count increments are significantly lower than expected. Although nonimmune causes of transfusion refractoriness are very common, HLA alloantibodies are the most important of the less frequent immune factors responsible for inadequate count increments. As universal leukoreduction decreases the occurrence of HLA antibody formation, antibodies to human platelet antigens (HPAs), an even less common immune factor, may rise proportionately. Carefully matched apheresis platelets can substantially improve platelet count increments in the setting of HLA and HPA alloantibody-mediated transfusion refractoriness. An evidence-based HPA testing strategy is described along with the incidence and specificity of HPA antibodies in platelet transfusion refractoriness. Optimal strategies to manage patients with HPA or combined HPA and HLA antibodies are presented. Ultimately, close cooperation between ordering physicians and the blood provider is critical in choosing the correct tests and assuring platelet availability during intensive support of these challenging patients. Immunohematology2009;25:119–124.