Patient selection and inclusion/exclusion criteria. (A) Patients with a cPRA of <50% were excluded because our institutional practice is to give random donor platelets in this setting. Generally, alloimmunization is suspected as a cause of PTR after 2 sequential platelet transfusions with poor count increment, however, this is not a strict criterion. Histograms of the total number (B) of platelet transfusions per patient among 2140 total platelet transfusions and the duration (C) of platelet transfusion support (encompassing the time between the first and the last documented transfusion), during the study period. The y-axis in each figure represents patient counts. cPRA, calculated panel reactive antibody; PTR, platelet transfusion refractoriness.