Immunohematology: Immune cytopenias and screening blood donors for immune response to infection

One of the most remarkable aspects of screening blood donors for evidence of their immune response to infectious agents is the size and scope of the undertaking. Some 3 million patients a year in America require transfusions, which are provided by about 13 million donations. Against this background, screening in the interests of ensuring transfusion safety for patients also represents a massive public health intervention from the standpoint of notifying and counseling donors about positive test results. For some markers, particularly HBsAg, anti-HIV, and anti-HCV, this is vitally important information. The chronic carrier of hepatitis B can be warned about possible health outcomes and close contacts can be offered vaccination. Many donors found to be truly positive for HIV antibodies were infected unwittingly and otherwise might not have been made aware of their infection. It is possible that similar benefits will accrue in the notification of donors found to be truly positive for antibodies to HCV. Many of these donors also were infected unwittingly. As better understanding of the value of treatment for the HCV-infected patient emerges, particularly with the use of interferon, early treatment of asymptomatic individuals may enable them to escape long-term complications of HCV infection. Although some progress is being made toward the viral inactivation of products for transfusion, particularly clotting factor concentrates, it is highly likely that the mainstay of transfusion safety will continue to be screening donors for markers of infectious disease. As was pointed out earlier, careful consideration must be given to the usefulness of additional donor screening. This is particularly true for rarely transmitted infectious diseases in which screening will result in further attrition of the donor base as a result of nonspecific test results.