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Alternative names
Indirect antiglobulin testDefinition Return to top
The indirect Coombs' test measures the presence of antibodies to red blood cells in the blood (see also Coombs' test - direct).
How the test is performed Return to top
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 Return to top
No special preparation is necessary.
Infants or young children:
The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following topics:
How the test will feel Return to top
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 Return to top
The indirect Coombs' test detects circulating antibodies against red blood cells (RBCs). The major use of this test is to determine if the patient has antibodies in the blood capable of attaching to RBCs. These antibodies are other than the major ABO system or the Rh type.
The test is only rarely used to diagnose a medical condition, but is essential for use by laboratories such as blood banks. Blood banks use the indirect Coombs' test to determine whether there is likely to be an adverse reaction to blood to be transfused.
Normal Values Return to top
No agglutination (absence of clumping of red blood cells) is normal.
What abnormal results mean Return to top
An abnormal indirect Coombs' test may indicate the presence of an antibody against an antigen that the body views as foreign:
If you have antibodies against your own RBCs, the indirect Coombs' test results may be abnormal, if there are excess antibodies beyond what your red blood cells can absorb. This may indicate autoimmune hemolytic anemia or drug-induced hemolytic anemia.
What the risks are Return to top
Special considerations Return to top
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others. Update Date: 8/16/2004 Updated 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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Page last updated: 28 October 2004 |