Indirect Antiglobulin Test

The indirect antiglobulin test (IAT) is a blood test which detects antibodies directed against red blood cell antigens. This is done in preparation for a blood transfusion, or during pregnancy and at delivery to avoid problems or make sure there are no problems.

The IAT looks for circulating antibodies directed against red blood cells (RBCs). RBCs normally have structures on their surface called antigens. You have your own individual set of antigens on your RBCs. These are inherited from your parents. If you have a blood transfusion, your body will recognize antigens on the new blood is not your own. Your plasma cells then may produce antibodies to attack these foreign antigens and red blood cells. People who have many transfusions are more likely to make antibodies to RBCs because they are exposed to more foreign RBC antigens.

When a baby inherits antigens from its father that are not on its mother's RBCs, the mother can produce antibodies against the foreign antigens on her baby's RBCs inside the womb. This can cause hemolytic disease of the newborn, usually not affecting the first baby but may affect subsequent children.

The IAT detects the presence of these circulating RBC antibodies in the fluid portion of the blood (plasma). The first time a person is exposed to a foreign antigen, by transfusion or pregnancy, their cells may recognize the need to produce an antibody directed against the foreign RBCs but does not usually have the time to make enough antibody to actually destroy the foreign cells. When the next transfusion or pregnancy occurs, the antibody may be strong enough to attach to the transfused RBCs or if a woman is pregnant, to her baby's RBCs, causing the red cells to have a shortened survival time.


No preparation or fasting is necessary. A blood sample is drawn from a vein in your arm.


Negative; no agglutination.

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.


Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.


It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.