Leukoreduction filtration of blood with sickle cell trait.

Leukoreduction of cellular blood products by filtration has been shown to decrease the incidence of febrile nonhemolytic transfusion reactions, transmission of leukocyte-associated viruses, and HLA alloimmunization. However, the increasing popularity of leukofiltering blood products over the past few years has highlighted specific filtration failures associated with sickle trait (hemoglobin AS) blood. Sickle trait blood does not filter adequately, which leads to prolonged or incomplete filtration, often with a higher number of postfiltration leukocytes in the unit than the mandated minimal residual volume of <1 to 5 x 10(6). This review of the literature highlights various parameters that affect the adequacy of filtration of blood products, including effects of temperature, pH, osmolarity, type of anticoagulant, time of storage, and oxygen saturation of the blood unit. A combination of these factors likely contributes to the frequent filtration failure of sickle trait products. Although blood units are not routinely screened for sickle cell hemoglobin, administration of units with sickle trait red blood cells can be disadvantageous to certain patient populations. This review concludes with a discussion of different approaches to screening blood units for sickle cell trait.