Although leukocytes are a normal inclusion with whole blood collection they are actually considered a contaminant of the other blood components such as PRBC’s and platelets. They have increasingly been recognized as the cause or contributors to many transfusion reactions such as immunologically-mediated effects, infectious disease transmission (CMV) and reperfusion injury. Of these reactions the immunological mediated effects are the most common and include febrile non-hemolytic reactions, platelet refractoriness, and transplant rejection. Also included in this group are graft versus host disease (GVHD), immunosuppression and reactivation of viral disease.
Each unit of whole blood contains about 2 to 5 x 109 leukocytes (2 to 5 billion). With leukocyte filtering a 99.9% reduction can be obtained, leaving residual leukocyte counts below 5 x 106. If it were not for cost leukoreduction would likely be performed on all transfusion components. Currently it is recommended that chronically transfused patients, potential transplant recipients, patients with acute leukemia, patients with previous transfusion reactions, CMV seronegative at-risk patients, and patients undergoing cardiac surgery or oncology surgery should receive leukoreduced blood components