Extended phenotyping of blood group antigens: Towards improved transfusion practices

Abstract

Even though the International Society of Blood Transfusion has defined 38 blood group systems, only ABO and RhD are matched while selecting a compatible unit for blood recipients of Indian origin. Genetic disparity between a donor and a patient with reference to minor blood group antigens creates the risk of alloimmunization. The presence of red blood cell alloantibodies further creates the potential for serologic incompatibility, makes the selection of appropriate units for future transfusion more difficult, delays blood transfusion, and presents the risk of hemolytic disease of the newborn. Hence, there is a need to carry out extended blood group typing for antigens of clinical importance among donors and patients so that prophylactic antigen-matched blood can be given to a patient. Provision of antigen-matched blood will help in management of alloimmunized transfused-dependent patients carrying alloantibodies and/or autoantibodies. Typing of blood group antigens among large number of donors will also help in the development of antigen-negative inventories, develop indigenous red cell panels, and identify rare donors. Selection of blood group antigens for typing is important as it may not be always feasible to phenotype all the antigens. Based on the prevalence and immunogenicity of an antigen in a population, specific antigens have to be selected for typing so that the risk of alloimmunization reduces by strategic level of antigen matching. The aim of this review is to highlight the need for extended blood group phenotyping in different case scenarios and the methods available to do so. This review was performed by searching for keywords such as blood transfusion, red cell alloimmunization, partial antigen matching, rare blood donors, multitransfused patients, transfusion in thalassemics, molecular blood group genotyping, serology, and reagent red cell panels in PubMed and Google databases.