A firm red bump may mean you have been infected with TB bacteria at some time. The size of the firm bump not the red area is measured 2 to 3 days after the test to find out the result. Your doctor will consider your chance of having TB when looking at the skin test site. Results of the test depend on your risk for TB. If you are in a high-risk group, a smaller bump is considered a sign of infection. People at low risk for having TB need to have a larger bump to be diagnosed with a TB infection.
This includes people who have HIV, those who have had close recent contact with a person who has active TB, and those who have symptoms or a chest X-ray that shows TB.
Other people at high risk for TB include those who take corticosteroid medicines for a long time and people who take biologics. These are used to treat rheumatoid arthritis and Crohn's disease.
This includes people who have recently moved from or traveled in a country with a high rate of TB; those who use illegal drugs by injection intravenous drug users ; people who live in nursing homes; workers in hospitals, nursing homes, schools, and prisons; children younger than 4 years old; children ages 4 to 18 who are exposed to high-risk adults; and homeless people.
No firm bump forms at the test site, or a bump forms that is smaller than 5 mm 0. A firm bump that is 5 mm 0. A firm bump that is 10 mm 0. A firm bump that is 15 mm 0. 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. More tests—such as a chest X-ray, a sputum culture , or both—are usually done to see if you have an active TB infection. Current as of: September 23, Author: Healthwise Staff. Medical Review: E. This information does not replace the advice of a doctor.
Healthwise, Incorporated, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content. The Mantoux tuberculin skin test is a test to check if a person has been infected with TB bacteria. Using a small needle, a health care provider injects a liquid called tuberculin into the skin of the lower part of the arm.
When injected, a small, pale bump will appear. The person given the TST must return within 2 or 3 days to have a trained health care worker look for a reaction on the arm where the liquid was injected. The health care worker will look for a raised, hard area or swelling, and if present, measure its size using a ruler.
Redness by itself is not considered part of the reaction. The TST result depends on the size of the raised, hard area or swelling. If a TST is positive, additional tests are needed. Blood is collected into special tubes using a needle. The blood is delivered to a laboratory as directed by the IGRA test instructions. The laboratory runs the test and reports the results to the health care provider. This can be for any situation where a TST is recommended. There are rare exceptions when results from both tests may be useful in deciding whether a person has been infected with TB.
Certain people should be tested for TB bacteria because they are more likely to get TB disease, including:. Factors in selecting which test to use include the reason for testing, test availability, and cost. If a person is found to be infected with TB bacteria, other tests are needed to see if the person has TB disease. Learn about the relationship between perimenopause and depression. Discover the links between mood swings, depression, and fluctuating levels of….
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