[Washing and filtration of blood components: which indications are established?]

The washing of cells in blood components for transfusion is necessary (1) in cases of severe incompatibility to constituents of plasma in these components and (2) in cases of maternal antibodies to blood cells of the child when the child needs maternal blood components, e.g. in many cases of neonatal alloimmune thrombocytopenia. A single washing step is recommended in certain cases: paroxysmal nocturnal hemoglobinuria and T activation of red blood cells. There is no indication that components should be washed in cases of autoimmune hemolytic anemia. There are well-documented data which propound the necessity of filtering blood components in order to reduce the leukocyte content aiming at the prevention of a primary immune response to HLA antigens, of repeated febrile transfusion reactions caused by leukocyte antibodies and of the transmission of cytomegalovirus via blood components. Some observations suggest that the same type of filtration also should be carried out on blood components given to patients with paroxysmal nocturnal hemoglobinuria.