The costs of blood transfusion are particularly complex to assess because of the many factors that have to be taken into consideration (blood collection and screening for pathogens; blood component processing, including leukoreduction, storage, transport to the transfusion facility; administration of blood to the patient; management of potential short-and long-term transfusion-related side effects) [84] . The subtype of the blood unit also may play a role because some products, such as CMV-negative or autologous units, are costlier than classical allogeneic RBCs. Consequently, studies in this field have given extremely varied results, which are not easily comparable.