Leukocyte-reduced blood components: laboratory and clinical aspects

From a semantic viewpoint, it is obvious that “red cell concentrates” should contain red cells only, and the same is true for platelet concentrates—they should contain platelets and no other cells (e.g., contaminating leukocytes). Viable donor leukocytes contaminate blood components and are linked to a wide variety of acute and long-term transfusion complications, including febrile transfusion reactions, alloimmunization, transfusion-associated graft-versushost disease (TA-GVHD), immunomodulation, and transmission of infectious diseases. Consequently, removal of leukocytes from these concentrates should be an obvious consideration to diminish these complications. By definition, a unit of leukocyte-reduced (LR) blood or blood component must contain no more than 1× 10 according to European requirements and less than 5× 10 according to US requirements. In practice, there is no easy method to fulfil these requirements. For cellular blood components, an additional inproduction step as filtration is needed to obtain a low level of contaminating leukocytes. For apheresis methods, some techniques provide significant leukocyte depletion of the red cell and platelet units collected, although all subsets of leukocytes are not reduced to the same degree. The indications for prescribing LR blood components are not universally accepted. The guidelines for patients needing LR cellular blood components include patients who need chronic transfusions, patients with severe febrile transfusion reactions, patients with acute leukemia, patients needing cytomegalovirus (CMV)-negative blood components, and patients undergoing cardiac surgery. Some centers also include patients undergoing surgery in general in the guidelines, and some hospitals provide LR components to all pediatric transfusions. As the list of indications for LR components increases, many centers have implemented universal leukocyte reduction (ULR) to avoid difficulties with having two different inventories. Some countries in Europe opted for prestorage leukoreduction as a precautionary measure against variant Creutzfeldt– Jakob disease (vCJD), thus implementing ULR. In other countries, it was considered that more research was needed to justify the cost related to leukocyte reduction of all cellular components. The cost issue is essential, and some scientists argue that increased cost is the only argument against ULR. In the developing countries, the increased cost makes implementation of filtration procedures impossible. In summary, even among countries with high healthcare costs, various guidelines are followed concerning indications for LR cellular blood components. Thus, there is a need to highlight different aspects of leukocyte contamination of cellular blood components.