Test Overview A tuberculin skin test (also called a Mantoux tuberculin test) is done to see if you have ever been exposed to tuberculosis (TB). The test is done by putting a small amount of TB protein (antigens Mycobacterium tuberculosis ), your skin will react to the antigens by developing a firm red bump at the site within 2 or 3 days.
The TB antigens used in a tuberculin skin test are called purified protein derivative (PPD). A measured amount of PPD in a shot is put under the top layer of skin on your forearm. This is a good test for finding a TB infection. It is often used when symptoms, screening, or testing, such as a chest X-ray
A tuberculin skin test cannot tell how long you have been infected with TB. It also cannot tell if the infection is latent
Why It Is Done
A tuberculin skin test is done to find people who have tuberculosis (TB), including:
People who have been in close contact with someone known to have TB. Health care workers who are likely to be exposed to TB. People with TB symptoms, such as an ongoing cough, night sweats, and unexplained weight loss. People who have had an abnormal chest X-ray. People who have had a recent organ transplant or have an impaired immune system human immunodeficiency virus (HIV) A tuberculin skin test should not be done for people:
With a known TB infection. Who have had a previous severe reaction to the TB antigens. Who have a skin rash that would make it hard to read the skin test. How To Prepare
In general, there's nothing you have to do before this test, unless your doctor tells you to.
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How It Is Done
For a tuberculin skin test, you sit down and turn the inner side of your forearm up. The skin where the test is done is cleaned and allowed to dry. A small shot of the tuberculosis antigen (purified protein derivative, or PPD) is put under the top layer of skin
How It Feels
You may feel a quick sting or pinch from the needle.
Risks
There is a very slight risk of having a severe reaction to the tuberculin skin test, especially if you've had tuberculosis (TB). An allergic reaction
You cannot get a TB infection from the tuberculin skin test. That's because no live bacteria are used for the test.
A tuberculin skin test is safe during pregnancy or breastfeeding.
Results
Redness alone at the skin test site usually means you haven't been infected with TB bacteria. A firm red bump may mean you have been infected with TB bacteria at some time. The size of the firm bump
Results of the test depend on your risk for TB. If you are at higher risk, a smaller bump is considered a sign of infection. People at lower risk for having TB need to have a larger bump to be diagnosed with a TB infection.
Mantoux tuberculin skin test Normal (negative results):
No firm bump forms at the test site, or a bump forms that is smaller than 5 mm (0.2 in.)
Abnormal (positive results):
A firm bump that is 5 mm (0.2 in.) or larger in size suggests a TB infection.
A positive reaction can usually be seen for about 1 week.
A positive tuberculin skin test doesn't mean you have contagious (active) TB. The test can't tell whether you have active or inactive (latent) TB. It also can't tell the difference between a TB infection and a TB vaccination (BCG vaccination culture
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Current as of: April 30, 2024
