Blood Test in Immunohematology and Blood Banking

Abstract

Blood samples for ABO and Rh (D) grouping and for all routine hematology tests are collected daily from different collection points, from admitted and outdoor patients. Preanalytical variables can alter the analysis of blood-derived samples. Prior to the analysis of a blood sample, multiple steps are necessary to generate the precise result. ABO and Rh (D) blood grouping are the first steps of laboratory procedure before proceeding for the crossmatching of recipient’s blood with group compatible donor’s blood. In routine clinical analysis, there is a wide range of established procedures and practices for ABO and Rh (D) typing where nearly all of them deal with the formation of agglutinates. These techniques differ from each other in terms of sensitivity, reagents and equipment required, the time of operation, and analysis. Two basic methods to observe the hemagglutination reaction in ABO and Rh (D) typing are the slide and test tube method with their inbuilt advantages and drawbacks. The slide test for both ABO and Rh (D) grouping has good sensitive method among others, for blood group determination, and due to its prompt results, it is widely acceptable and valuable in emergency and routine cases. In comparison to the slide test, the tube test is more sensitive and reliable; therefore, it can be used conveniently for blood transfusion crossmatching procedure and when sufficient time is available for testing. Errors in ABO and Rh (D) grouping could be due to factors related to red cells and factors related to serum. Most of these errors occur when blood grouping standards are unavailable or misinterpreted. The final criteria of whether donor blood is safe to a patient depends on ABO and Rh grouping and running of compatibility test to see any signs of compatibility or incompatibility. Under most circumstances, if grouping and Rh typing tests have been performed accurately and if the donor blood of the same group and Rh type has been selected for testing and transfusion, they will be found to be compatible. Direct antiglobulin test is indicated in investigation of the hemolytic transfusion reactions whether it is acute or chronic. It requires posttransfusion blood sample. Indirect antihuman globulin test (IAT) to detect the sensitization of red cells is done in the laboratory (in vitro). Indirect antiglobulin test detects whether an Rh-negative woman married to Rh-positive husband has developed anti-Rh antibodies in her blood. The antibody screening test is performed to detect the presence of unexpected antibodies, especially alloantibodies in the serum to antigens of the non-ABO blood group system: Duffy, Kell, Kidd, MNS, P, and certain Rh types that are considered clinically significant. Naturally occurring anti-A and anti-B are the only RBC antibodies in normal human serum or plasma. Antibody titration (ABT) of anti-D is a semiquantitative method used to detect the reactivity of antibodies present in the patient’s plasma to screen for risk of hemolytic disease of the fetus and newborn.