Coombs Test - Indirect Test

Indirect Coomb's Test is a blood test that is used to determine the compatibility of the antibodies that are present in the blood of different people. Indirect Coomb's test is also known as indirect antiglobulin test or IAT and it looks at the plasma of the blood and detects certain antibodies present in the plasma. The test is conducted before a blood transfusion to ensure that donor's blood is compatible with the recipient's blood. The test is also done during the early stages of pregnancy to determine Rh factor of the mother's blood.

It is not required for the patient to be fasting before the test. If you take any regular medications, inform the doctor. You may have to stop them for a few days before the test. Also inform the lab if you are allergic to latex. Only a few milliliters of blood is required for the test. However, if you do have a history of feeling light headed or faint upon blood collection, do inform the lab about the same. Wear a sleeveless or half sleeve shirt or top or a shirt whose sleeves can be rolled up for collecting blood.

Indirect Coomb's test detects the antibodies present in the serum or plasma of the blood. An abnormal result in an indirect Coomb's test can be an indication of any of the following: If the test was done to check compatibility during transfusion, an abnormal result indicates that the blood does not match and should not be transfused. If the test gives negative result while administered on pregnant women, it indicates that the Rh type of the mother and infant are different and the mother's immune system will attack the child's during labor. It can also indicate hemolytic anemia due to an autoimmune reaction. An abnormal result may also be due to drug toxicity.

The blood collection for indirect Coomb's test can be performed at a lab or at a clinic. A vein is selected for drawing blood. A tourniquet is secured above the vein. The skin is cleaned using an alcohol pad. A needle is inserted in to the vein and blood is collected in one or two tubes. The tubes are labeled with your name or ID and then send to the laboratory for testing.