Blood grouping

Introduction Blood grouping is the laboratory process of identifying specific inherited antigens present on the surface of an individual's red blood cells (RBCs). These antigens determine a person's blood group and play a critical role in blood transfusion, organ transplantation, pregnancy, forensic medicine, and immunohematology. Although hundreds of red-cell antigens are recognized, the ABO and Rh blood group systems are the most important in routine clinical practice. Modern transfusion medicine depends heavily on accurate blood grouping because transfusion of incompatible red cells can cause severe, potentially fatal hemolytic reactions. The scientific foundation of blood grouping was established by Karl Landsteiner, who discovered the ABO blood group system at the beginning of the twentieth century after observing that serum from some individuals caused the red cells of others to agglutinate. His work demonstrated that differences in red-cell antigens and naturally occurring antibodies were responsible for many previously unexplained transfusion reactions. The discovery transformed blood transfusion from a highly hazardous procedure into an increasingly safe therapeutic practice. Blood grouping is therefore more than simply identifying whether an individual is A, B, AB, or O. It involves understanding antigen-antibody reactions, inheritance, laboratory techniques, compatibility testing, and the clinical consequences of incompatibility.