Direct and indirect antibody tests

direct antibody Test

Looks for the presence of IgG and/or complement on the RBCs. This causes hemolysis and can be due to an autoimmune disease, transfusion reaction, etc.

Indirect antibody Test

This is used when cross-matching people for a blood transfusion. It tests patients for the presence of unexpected alloantibodies (anti-D, anti-E, anti-C, anti-Kell, anti-Duffy). This is just a screen, if it is positive, you can then test for specific antibodies and then only transfuse blood that is negative for those specific antigens.

* 19/06/2013 Please excuse the doodle for saying “agglutination” though it is testing by agglutinating, the “A” in DAT stands for antibody. Thanks Robina for pointing this out!

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3 thoughts on “Direct and indirect antibody tests

  1. Very good depiction of the DAT and IAT . One comment is that I believe Coombs reagent is an IgG rather than an IgM, since you have to attach the antibody at 37C. But I could be wrong. Thank you

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