Coombs' Test

What is the Coombs' test?

The Coombs' test is a blood test of the immune system. There are 2 types of Coombs' tests:

• direct Coombs' test (also called the direct antiglobulin test)
• indirect Coombs' test (also called the indirect antiglobulin test).

Why is this test done?

The Coombs' test is done to see if your red blood cells are being attacked and broken down by your body's immune system. It looks for antibodies against red blood cells. It may be done to help the diagnosis of some medical problems, such as jaundice, anemia, lupus, or mononucleosis. A pregnant woman may have this test if there is a concern that the mother's antibodies may destroy red blood cells in her newborn. If you are going to have a blood transfusion, it may be done to help check for blood that will be a good match.

How do I prepare for this test?

The Coombs' test is a simple blood test. There is no special preparation needed for this test.

How is the test done?

A small amount of blood is taken from your arm with a needle. The blood is collected in tubes and sent to a lab. In the lab it is examined for clumping of cells (agglutination).

Having this test will take just a few minutes of your time. There is no risk of getting AIDS, hepatitis, or any other blood-borne disease from this test.

How will I get the test result?

Ask your healthcare provider when and how you will get the result of your test. It may take a couple of days to get the results of your blood work.

What does the test result mean?

If there is no clumping of cells the test result is negative and normal.

If there is clumping of cells, the result if positive.

Some of the conditions that have a positive Coombs' test are:

• systemic lupus erythematosus (lupus)
• infectious mononucleosis (mono)
• autoimmune anemia or drug-induced hemolytic anemia
• syphilis
• chronic lymphocytic leukemia
• blood transfusion incompatibility
• mother and newborn blood incompatibility.

What if my test result is not normal?

Test results are only one part of a larger picture that takes into account your medical history and current health. Sometimes a test needs to be repeated to check the first result. Talk to your healthcare provider about your result and ask questions.

If your test results are not normal, ask your healthcare provider:

• if you need additional tests
• what you can do to work toward a normal value
• when you need to be tested again.

Written by Lee A. Mancini, MD, CSCS, CSN
Published by RelayHealth.
© 2009 RelayHealth and/or its affiliates. All Rights Reserved.