Independent roles for platelet crossmatching and HLA in the selection of platelets for alloimmunized patients

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Abstract
Although HLA-matched platelets are frequently requested for alloimmunized patients, recent evidence has indicated that 1-hour posttransfusion platelet increments in these patients are specifically sensitive to crossmatch compatibility. To determine the extent of advantage gained by use of single-donor apheresis (SD) platelets selected on the basis of HLA match when crossmatch-compatible SD platelets were available, a total of 220 platelet transfusions given in the absence of individually determined significant nonimmune factors were analyzed in a well-characterized cohort of platelet-refractory patients. Platelets were selected by solid-phase crossmatch from a small donor pool of relatively poor HLA matches or, upon request, ordered as HLA-matched and later crossmatched. Alloimmunized patients responded better to SD platelets selected on the basis of HLA than to pooled platelet concentrates or SD platelets selected at random, although most of the benefit was limited to the 57-percent subset of good HLA matches. Crossmatch-compatible SD platelets provided similar posttransfusion platelet increments independent of the HLA match. None of 31 crossmatch-incompatible SD platelets transfused provided an adequate increment, including 13 that were ordered as HLA-matched platelets. No benefit could be demonstrated from requesting that SD platelets be HLA-matched when crossmatch-compatible SD platelets were available.