The TB (Tuberculosis) Skin Test (Mantoux)This fact sheet gives information about how the skin test is given and read, and what the results mean. Show
On this page:
The tuberculosis (TB) skin test, sometimes called a "Mantoux," is a simple, harmless way to find out if you have latent TB infection.  What is latent TB infection?There are two phases of TB. Both phases can be treated with medicine. When TB germs first enter your body, they cause latent TB infection. Without treatment, latent TB infection can become active TB disease. Anyone can get TB because it spreads from one person to another through the air.
How can I tell if I have latent TB infection?A TB skin test ("Mantoux") can show if you have latent TB infection. You could have latent TB infection if you have ever spent time close to someone with active TB disease (even if you didn't know they were sick). Your health care provider will use a small needle to inject some harmless testing fluid (called "tuberculin") under the skin on your arm. Your health care provider MUST check your arm 2 or 3 days after the TB skin test, even if your arm looks OK to you. If you have a reaction to the test, it will look like a raised bump. Your health care provider will measure the size of the reaction. If there is a bump, it will go away in a few weeks. How do I take care of my arm after the TB skin test?
Don't be afraid to be tested. TB can be cured! What if my TB skin test is negative?The test is "negative" if there is no bump (or only a very small bump) at the spot where the fluid was injected. A negative TB skin test usually means that you don't have TB. In some situations, you may need to have another TB skin test later. What if my TB skin test is positive?The test is "positive" if there is a bump of a certain size where the fluid was injected. This means you probably have TB germs in your body. Most people with a positive TB skin test have latent TB infection. To be sure, your doctor will examine you and give you a chest x-ray. You may need other tests to see if you have active TB disease. Protect your health
and the health of your family - get a TB skin test! You should have a TB skin test if:
What if I've had BCG vaccine?Even if you have had BCG vaccine, you can have a TB skin test.
You can have a TB skin test, even if you have had BCG vaccine! Which are reasons why a falseFalse-negative TST reactions may occur if the TB infection occurred within 8 weeks of skin testing. False-negative Anergy HIV-infected people, other people with weakened immune systems, severe TB disease, and some viral illness (e.g., measles, mumps, and chicken pox) or bacterial infection (e.g., typhoid, etc.)
Are false positives common for TB?In 12 studies of 12,728 subjects vaccinated after their first birthday, 5314 (41.8%) had a false-positive TST of 10+ mm, and 191/898 (21.2%) after 10 years. Type of tuberculin test did not modify these results.
Which conditions may cause a falseThe TST relies on a competent delayed-type hypersensitivity reaction to the injected tuberculin. Generalised or antigen-specific immunosuppression (anergy) may cause false-negative TST.
What does a positive TB skin test indicate?A positive TB skin test or TB blood test only tells that a person has been infected with TB bacteria. It does not tell whether the person has latent TB infection (LTBI) or has progressed to TB disease.
|
