Coombs’ test

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Results

Coombs’ test - direct

Definition:

The direct Coombs' test measures the presence of antibodies on the surface of red blood cells.

How the test is performed:

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

How to prepare for the test:

No special preparation is necessary for this test.

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing or a bruise may develop at the site where the needle was inserted.

Why the test is performed:

The direct Coombs' test is used to detect autoantibodies against your own red blood cells (RBCs). Many diseases and drugs (quinidine, methyldopa, and procainamide) can lead to production of these antibodies.

These antibodies sometimes destroy red blood cells and cause anemia. This test is sometimes performed to diagnose the cause of anemia, jaundice, or abnormalities in the appearance of RBCs under the microscope.

Review Date: 8/16/2004
Reviewed By: Stephen Grund, M.D., Ph.D., Chief of Hematology & Oncology and Director of the George Bray Cancer Center at New Britain General Hospital, New Britain, CT. Review provided by VeriMed Healthcare Network.

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