[Clinical applications of leukocyte filters]

Leukocytes present in allogeneic blood components have been associated with adverse effects to the recipient. These include the development of febrile transfusion reactions, alloimmunization to human leukocyte antigens, graft-versus-host disease, and immunomodulatory effects. In addition, such leukocytes may be the vector of infectious agents such as CMV, HTLV-I/II, and EBV. It has been postulated that the use of white blood cell filters to reduce the leukocyte content in allogeneic blood products may minimize the occurrence of these biological adverse effects associated with leukocytes present in transfused blood products. However, it is still to be determined the clinical effectiveness of leukodepletion. It has been suggested that 1 log10 leukocyte reduction prevents febrile non-hemolytic transfusion reactions; that a 2 log10 reduction may prevent the transmission of viruses; and that a > or = 3 log10 reduction may be necessary to prevent platelet alloimmunization. However, because there are no data available as guidelines for the use of leukodepleted blood products for most clinical indications, the use of white cell filters should be restricted to selected patients for whom such data exist. Properly designed prospective clinical trials are necessary to provide data to help to define the cost-benefit of the clinical application of leukodepletion.