Depletion of white cells from platelet concentrates with a new adsorption filter

Removal of white cells (WBCs) from platelets may reduce alloimmunization to WBC antigens, prevent febrile reactions, and improve platelet increments in multiply transfused patients receiving HLA-matched platelets. A new surface-modified fibrous polyester filter was evaluated; it requires no special processing of pooled platelet concentrates and can be used at the patient's bedside. The studies were designed to measure WBC removal, platelet function, in vitro platelet recovery, and in vivo platelet survival. WBC mean removal was 99.8 percent +/- 0.56 (n = 37) when a pool similar in volume to 6 platelet concentrates was tested. The mean number of residual WBCs after filtration was 5.6 x 10(5). In vitro mean platelet recovery was 86.9 percent for a pool size of 6 units (n = 37). Clot retraction and platelet aggregation were unaffected by filtration. Survival studies of 111Indium-labeled platelets done with filtered autologous platelets showed no reduction in the normally expected survival. These studies indicated that the filter efficiently removes WBCs without substantially decreasing platelet number, survival, or function. This device offers the potential of considerably improving platelet transfusion therapy.