What is the principle of the Direct Antiglobulin Test (DAT)?

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What is the principle of the Direct Antiglobulin Test (DAT)?

The direct antiglobulin test detects in vivo sensitization of red blood cells with IgG and/or complement. In practice, a patient’s red cells are washed to remove unbound proteins, then anti-human globulin (Coombs reagent) is added. If the red cells have been coated in the body with IgG or with complement (such as C3), the anti-human globulin will bind to those surface antibodies or complement and cause the cells to agglutinate. A positive result shows that immune components are already attached to the patient’s red cells, which helps identify conditions like autoimmune hemolytic anemia, transfusion reactions, or hemolytic disease of the newborn. This differs from tests that look for antibodies in serum (the indirect antiglobulin test) or from tests that measure hemolysis in plasma; those assess different aspects and do not specifically indicate in vivo red cell sensitization.

The direct antiglobulin test detects in vivo sensitization of red blood cells with IgG and/or complement. In practice, a patient’s red cells are washed to remove unbound proteins, then anti-human globulin (Coombs reagent) is added. If the red cells have been coated in the body with IgG or with complement (such as C3), the anti-human globulin will bind to those surface antibodies or complement and cause the cells to agglutinate. A positive result shows that immune components are already attached to the patient’s red cells, which helps identify conditions like autoimmune hemolytic anemia, transfusion reactions, or hemolytic disease of the newborn. This differs from tests that look for antibodies in serum (the indirect antiglobulin test) or from tests that measure hemolysis in plasma; those assess different aspects and do not specifically indicate in vivo red cell sensitization.

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