Transfusion medicine reviews
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Microchimerism, the coexistence of genetically disparate populations of cells in a receptive host, is well described in both clinical and physiological settings, including transplantation and pregnancy. Microchimerism can also occur after allogeneic blood transfusion in traumatically injured patients, where donor cells have been observed decades after transfusion. To date, transfusion-associated microchimerism (TA-MC) appears confined to this clinical subset, most likely due to the immune perturbations that occur after severe trauma that allow foreign donor cells to survive. ⋯ There are, however, hypothesized links to transfusion-associated graft vs host disease that may be unrecognized and consequently underreported. Microchimerism in other settings has gained increasing attention owing to a plausible link to autoimmune diseases, as well as its diagnostic and therapeutic potential vis-a-vis antenatal testing and adoptive immunotherapy, respectively. Furthermore, microchimerism provides a tool to further our understanding of immune tolerance and regulation.
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Transfusion-related acute lung injury (TRALI) is a major cause of transfusion-related morbidity and mortality. Although the pathogenesis of TRALI is incompletely understood, substantial data from hemovigilance systems, large case series, clinical trials, and animal models have identified antileukocyte antibodies as a major precipitant and have contributed to the development of concrete interventions to reduce the risk of TRALI. This review presents the clinical data supporting specific donor management strategies to reduce TRALI risk and their observed clinical efficacy. Novel strategies that use the donor health questionnaire combined with testing are discussed, and important challenges that remain going forward are explored.
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Large scale red blood cell (RBC) antigen genotyping of donors is currently well developed. There is scarce information, however, to select patients who might benefit from preemptive extended RBC antigen-matched transfusions. Female sex has been proposed as a risk factor for RBC alloimmunization after transfusion. ⋯ This is likely explained by more exposure to immunizing events through pregnancy and/or transfusions in females with sickle cell disease. The results support the current policy implemented in many countries for Rhesus/Kell matching in patients with a hemoglobinopathy irrespective of sex. Thus, based solely on sex difference, the results do not justify recommending additional matching for women, besides preemptive K and c antigen matching for women during the (pre-) fertile age, as already applied in many European countries for the prevention of fetal morbidity.
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Blood safety remains an important public health concern in Africa where lack of availability or provision of unsafe blood adversely impacts morbidity and mortality in the region. In recognition of this shortfall, the World Health Organization (WHO) established a goal of regional blood safety by 2012 through improved "organization and management, blood donor recruitment and collection, testing of donor blood as well as appropriate clinical use of blood" (Tagny et al: Transfusion. 2008;48:1256-1261; Tapko et al: Status of Blood Safety in the WHO African Region: Report of the 2006 Survey http://www.afro.who.int/en/divisions-a-programmes/dsd/health-technologies-a-laboratories.html. Brazzaville, Republic of Congo: WHO Regional Office for Africa; 2006). ⋯ In a setting where transfusion oversight is still being improved, transfusion-transmitted infections are of real concern. The high prevalence of some transfusion-transmissible agents such as hepatitis B virus and HIV in the general population means that some infected blood units escape detection by even well-performed laboratory testing, resulting in potential downstream transmission to patients. The spectrum of transfusion-transmitted infection include conventional as well as exotic pathogens, many of which are endemic to the region, thereby imparting ongoing challenges to recruitment and testing strategies.
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In the recent years, thromboelastography has become a popular monitoring device for hemostasis and transfusion management in major surgery, trauma, and hemophilia. Thromboelastography is performed in whole blood and assesses the viscoelastic property of clot formation under low shear condition. ⋯ Furthermore, fibrinogen levels and platelet counts have a major influence on thromboelastographic variables. In addition, differences in patient populations, devices, and preanalytical conditions contribute to some conflicting findings in different studies.