2 Cellular blood components: preparation, preservation, leukodepletion and indication

Blood components have replaced whole-blood transfusion because they allow better maintenance of quality, more effective use of the donor's blood and more appropriate dosage to the patients. The techniques for the preparation and storage of components, both from whole blood and via apheresis, have developed gradually. The oxygen-releasing capacity of the erythrocytes is still influenced negatively even after short storage with currently used systems, but better methods have been described. Leukocyte removal from red cell and platelet preparations results in different degrees of purity. Filtration as well as some apheresis techniques have improved in recent years so that the aim, <5 × 10⁶ leukocytes per transfusion, can be achieved confidently. Transfusion-associated graft-versushost disease requires attention. Collection of haematopoietic stem cells from peripheral blood for transplantation has become an important new task. Bacterial contamination, being a greater problem in platelet concentrates than earlier believed, can be detected by testing and probably soon counteracted by decontamination.