Red Blood Cell Antibody Screen
Reviewed
Also called: Antibody Screen, Indirect Antiglobulin Test, Indirect Coombs Test, IAT
This blood test looks for RBC antibodies that your immune system makes when exposed to foreign red blood cells. It is used before blood transfusions to help match donor blood and during pregnancy to check for antibodies that could harm the fetus.
Specimen: Blood sample from a vein in your arm
Why this test may be ordered
- Before a blood transfusion to select compatible donor blood
- During pregnancy as part of routine prenatal testing to detect antibodies that could cause fetal anemia
Preparation and collection
No special preparation needed.
A health care professional will take a blood sample from a vein in your arm. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
Results are interpreted by your healthcare provider based on your situation. The following patterns are based on the test's purpose.
- Negative: No RBC antibodies were found. Limitation: If you have had RBC antibodies in the past, they may be present at levels too low to detect on this test. Next step: Routine
- Positive: One or more RBC antibodies were found in your blood. Limitation: A positive result does not specify which antibodies are present. Further testing is needed to identify the specific antibodies. Next step: Prompt
- Once your body makes RBC antibodies, you will always have them, but they may be too few to show up on a test.
- A positive result requires additional tests to identify the specific antibodies.
- If you have had a previous positive RBC antibody screen, inform your provider, especially before a blood transfusion or during pregnancy.
What to do next
If you have questions about your results, talk with your provider.
- What do my results mean for my blood transfusion or pregnancy?
- If I am Rh-negative, will I need an injection to prevent making Rh antibodies?
- Do I need additional testing to identify specific antibodies?
Evidence source
U.S. National Library of Medicine: Red Blood Cell Antibody Screen