antiglobulinecrossmatch

The antiglobulin test, commonly known as the Coombs test, is a serologic assay used to detect antibodies or complement proteins bound to red blood cells. It is widely used in transfusion medicine and in the evaluation of immune-mediated hemolytic conditions. The test uses anti-human globulin (AHG) reagents to reveal immune coating of erythrocytes and to guide diagnosis and management.

In the direct antiglobulin test (DAT), washed patient red blood cells are incubated with AHG reagent. If antibodies or complement are already bound to the red cells in vivo, the AHG causes agglutination, indicating a positive result. A positive DAT supports diagnoses such as autoimmune hemolytic anemia, hemolytic disease of the newborn, or transfusion reactions, depending on the clinical context and additional testing.

In the indirect antiglobulin test (IAT), patient serum is incubated with a panel of donor red blood cells to allow alloantibodies to attach to antigens on the cells. After washing, AHG is added. Agglutination indicates the presence of antibodies in the serum that could cause a transfusion reaction or hemolytic disease of the newborn if matching antibodies are present.

Core uses include pretransfusion antibody screening and compatibility testing, evaluation of suspected immune-mediated hemolysis, and screening of pregnant patients for antibodies that could affect the fetus. The test results require interpretation alongside clinical findings, as false positives and negatives can occur due to technical factors or recent transfusions. The Coombs test has remained a standard tool in immunohematology since its development in the mid-20th century.