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Indirect Antiglobulin Blood Test

Last updated July 15, 2019

Approved by: Maulik P. Purohit MD MPH

The Indirect Antiglobulin Test (IAT) determines the presence of antibodies that are circulating within the bloodstream, which are specific to red cell antigens.


What are the other Names for this Test? (Equivalent Terms)

  • IAT (Indirect Antiglobulin Test)
  • Indirect Anti-Human Globulin Test
  • Indirect Coombs Test

What is Indirect Antiglobulin Blood Test? (Background Information)

  • The Indirect Antiglobulin Test (IAT) determines the presence of antibodies that are circulating within the bloodstream, which are specific to red cell antigens. The red cell antigens are present on human red blood cells
  • The circulating antibodies that are directed against the red cell antigens, can be due to a variety of reasons, including blood transfusions and incompatibility in mother-baby blood types, in a pregnant or recently-delivered woman
  • These antibodies can cause hemolytic disease of newborns, which results in breakdown of newborn red blood cells. This causes anemia and jaundice in the newborns

What are the Clinical Indications for performing the Indirect Antiglobulin Blood Test?

The Indirect Antiglobulin Test is performed either as a workup (intensive diagnostic study) of a transfusion reaction, or as part of the workup during a pregnancy.

A transfusion reaction following a blood transfusion can result in a variety of symptoms, such as:

  • Change in blood pressure
  • Low back pain
  • Fever with chills
  • Reddish urine

How is the Specimen Collected for Indirect Antiglobulin Blood Test?

Sample required: Blood

Process: A needle is inserted into a superficial vein of the arm to collect the blood sample.

Preparation required: No special preparation is required prior to performing an Indirect Antiglobulin Test.

What is the Significance of the Indirect Antiglobulin Blood Test Result?

Significance of the Indirect Antiglobulin Test:

  • A positive IAT means that there are circulating antibodies present, which are directed against the red cells
  • Further testing to characterize the nature of these antibodies is important, in order to determine their significance
  • Some circulating antibodies are more harmful than others. A variety of tests can be performed to determine the specificity of these circulating antibodies

In pregnant women who are Rh negative, it is very important to do an IAT.

  • If the IAT is negative, then RhoGam (a kind of medicine) can be given to an Rh negative mother
  • If the mother is positive for IAT and if further testing determines that these antibodies are directed against the Rh antigen then, RhoGam injections may not have a beneficial effect
  • The management of a positive IAT depends upon the specificity of the circulating antibodies. A consultation with a pathologist is usually necessary to determine its significance

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

Please check back for periodic updates to our ‘physician approved content’.

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

References and Information Sources used for the Article:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Aug. 19, 2013
Last updated: July 15, 2019