Evaluation of DAT positive AIHA cases by elution study at a tertiary care centre in South India

The Direct Antiglobulin Test [DAT] is widely used in Immunohematological laboratory test because it is simple, quick and inexpensive test. It is performed when the presence of haemolysis and is the most important diagnostic tests for determining Immune Hemolytic Anemias. With this background this study was conducted, to evaluate the DAT positive cases Autoimmune Hemolytic Anemia [AIHA], along with antibody classes, severity and finally to perform elution studies to specify the antibody coated onto the red cells.

34 DAT positive AIHA cases with clinical and laboratory evidence of hemolysis were evaluated in this study. In these cases 25 warm Autoimmune Hemolytic Anemia [WAIHA]. 6 Cold Agglutinin Disease [CAD] and 3 Mixed AIHA. Our study suggests a significant association between the strength of DAT, the IgG class and subclass of Immunoglobulins either alone or in combination with other classes of immunoglobulins and/or complements. The specificity of auto and alloantibodies were identified by adsorption and elution techniques, which revealed exclusively anti-e in 6 cases of WAIHA and 5 cases with alloantibodies. The elution provides unbound RBCs for phenotyping and provide appropriate transfusion support for the needy patients.

In our study revealed a strong association between the severity of hemolysis and the strength of DAT, the IgG and subclass (IgG 1 & IgG 3) of IgG Antibodies either alone or in combination with other classes of Antibodies and/or complements. The autoantibody specificity had anti-e in 6 cases of WAIHA and 5 cases had clinically significant alloantibodies. The positive DAT with falling hematocrit, jaundice appear to be clinically helpful in identifying alloantibodies.