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Most hospital blood transfusion services perform routine pretransfusion compatibility tests (ABO/D typings, antibody detection tests and crossmatches) using standard test tube methods. Recently, alternative technologies, including microtiter plate methods, solid phase red cell adherence (SPRCA) assays, gel tests, microbead columns and affinity column assays have become available. While the increased sensitivity of these new serological technologies is an important advantage, cost savings and automated testing are also important benefits. Our hospital's Transfusion Service converted from manual test tube methods for compatibility testing to manual microtiter plate and SPRCA methods and, subsequently, to automated microtiter plate and SPRCA methods. The conversion was facilitated by using commercially-marketed reagent kits and a fully-automated blood typing analyzer. The automated blood typing system was linked electronically to a hand-held combination bar code reader/portable data terminal that enabled positive identification of patients' bar code wrist bands, personal identification badges, and bar code labels on patients' blood samples and blood components. This bar code identification system has been implemented in the hospital's outpatient Infusion Service. Thus, the conversion to microtiter plate and SPRCA assays enhanced transfusion safety not only by increasing the sensitivity of serological testing, but also by standardizing compatibility testing, supporting electronic record keeping, and linking the laboratory analyzer to a bar code identification system.

Patients with hematologic malignancies or aplastic anemia may have reduced responses to platelet transfusions after multiple transfusions of standard red blood cells or platelet components. This situation, conventionally described as 'refractoriness' to platelet transfusions, may result from immune or non-immune causes. Non-immune causes include fever, infections, hypersplenism, disseminated intravascular coagulation, antibiotics, or veno-occlusive disease. Immune causes include platelet-reactive alloantibodies, which are typically antibodies to human leukocyte antigens (HLA) or, less commonly, antibodies to human platelet antigens (HPA). Transfused HLA-matched platelets often have satisfactory posttransfusion survivals, but few transfusion services have the donor and logistical resources to sustain a prolonged course of platelet transfusions requiring four-antigen matches. The availability of commercially marketed kits for crossmatching samples of potential donors' platelets with a recipient's serum has facilitated donor-recipient matching. Also, platelet crossmatching may be used to select a suitable unit of from several candidates platelets that have been identified to be partial HLA matches. The high likelihood of decreased efficacy of platelet transfusions in HLA-alloimmunized recipients makes avoidance of exposure to HLA-bearing leukocytes a priority. This goal is facilitated by lowering transfusion 'triggers' for cellular blood components, particularly for prophylactic platelet transfusions, by reducing the leukocyte content of components by leukocyte-reduction filters and, possibly by ultraviolet-B irradiation of leukocyte-containing products.

Biochemical studies reveal that erythrocyte blood group antigens are the immunological expression of polymorphic and, frequently, biologically-active membrane structures. Some of these structures have been identified to be specific transport proteins, enzymes, or receptors for infectious agents. Certain erythrocyte phenotypes, for example, Rh(null), lack all or most antigens in a specific blood group system. Changes in erythrocyte morphology and function associated with these phenotypes provide insights into the roles of the corresponding proteins in the maintenance of membrane integrity. Other phenotypes, for example Oh, and p, also lack multiple blood group antigens, but the absence of changes in morphology or function in these erythrocytes suggests that their corresponding carbohydrate determinants are not essential for maintaining membrane integrity. Additional information on the function of erythrocyte membrane structures that express blood group antigens is likely to advance our understanding of the role of blood groups in health and disease.

Blood donations by emigrants or other travelers from distant lands require special attention for the prevention of transfusion-transmitted infections. The human immunodeficiency virus, type 1 (HIV-1) is only one of several bloodborne viruses that may be introduced into non-epidemic areas by transfusion and spread further by sexual intercourse, needles shared by drug users or mother-child transmission. Although transfusion-transmitted parasites, such as Trypanosoma cruzi, do not spread further in non-endemic areas in the absence of specific vectors, such unlikely infections may cause serious disease before a diagnosis is made. The challenges posed by transfusion-transmitted infections in a shrinking world require specific preventive strategies and enhanced clinical awareness for timely diagnosis and treatment.

The increasing use of normal donors for leukapheresis to provide granulocyte concentrates requires careful monitoring of recruitment and operational procedures to minimize donor health risks. Of 18,288 leuka- and leukaplateletphereses performed in American Red Cross regional blood services during a 12-month period, only 0.27% were discontinued because of acute donor reactions. None of these reactions had serious or long-term consequences for the donors. The potential toxicities of corticosteroids and hydroxyethyl starch, and the theoretical hazards of lymphocyte depletion, raise unanswerable questions concerning long-term safety, although no serious adverse reactions related to these factors have been observed. Critical factors for leukapheresis donor safety are: selective donor recruitment, adherence to operational protocols, and continuous and informed interest of physicians responsible for pheresis programs. Additional data are needed to assess the effects of repeated leukapheresis on donors and to establish rational guidelines for donor recruitment.