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Rubella Test

Risks

Blood test

There is very little chance of a problem from having a blood sample taken from a vein.

  • You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
  • In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
  • Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (such as Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

Results

A rubella blood test detects antibodies that are made by the immune system to help kill the rubella virus. The test for IgG antibodies is most common and is the test done to see if a woman who is pregnant or planning to get pregnant is immune to rubella.

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Rubella blood test1
Positive:

More than 10 international units per milliliter (IU/mL) IgG antibodies. A positive rubella IgG test result is good—it means that you are immune to rubella and cannot get the infection. This is the most common rubella test done.

Negative:

Less than 7 IU/mL IgG antibodies and less than 0.9 IgM antibodies. This means you are not immune to rubella. If you are a woman thinking about getting pregnant, talk with your doctor about getting a rubella vaccine before pregnancy.

A test for rubella IgM antibodies is done only if the doctor suspects you have a current rubella infection. More than 1.1 IU/mL IgM antibodies means you had a recent rubella infection or you have a current infection.1

What Affects the Test

There are no factors that would interfere with the test or the accuracy of the results.

What To Think About

  • If a woman who wants to become pregnant has not had rubella, she can receive a shot (vaccination) to help protect her against getting the disease. But she must wait 1 month after she gets the shot before becoming pregnant to fully protect her baby.
  • A woman should not get a rubella shot while she is pregnant, and she should avoid people who have or may have rubella.
  • A rubella virus culture is not often done because it is a more difficult test.
  • Exposure to rubella in the third trimester may not be as serious since the baby (fetus) is fully developed. But these babies can have the infection and be contagious.
  • If congenital rubella is suspected, both the mother and her baby need blood tests.

WebMD Medical Reference from Healthwise

Last Updated: August 31, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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