What happens if i scratched my tb test

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Updated visitor guidelines. You are here Home » Tuberculin Skin Test. Top of the page. 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. 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 , such as those with 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.

How It Is Done For a tuberculin skin test, you sit down and turn the inner side of your forearm up. Low-risk group includes people who do not have any possible exposure to TB listed in the other risk groups. A positive reaction usually remains visible for about 1 week.

Taking medicines that suppress the immune system, such as corticosteroids. Conditions that weaken the immune system, such as HIV infection or cancer. The result also may be affected if a person is severely malnourished. Some vaccinations for infections, such as measles, mumps, rubella, polio, or chickenpox, given within 6 weeks before the tuberculin test.

A recent infection with one of these viruses can also interfere with test results for a short period of time. The skin test also may be positive if the person has an infection caused by a mycobacterium other than the one that causes TB. A very recent TB infection. It takes 2 to 10 weeks for the immune system to react to TB bacteria.

Age younger than 3 months old. The booster effect is a weak or no reaction to one TB skin test followed by a strong reaction from a second test. But the strong reaction to the second test does not mean that the person has just become infected with TB. Instead, the reaction may be because of: A TB infection that occurred long ago.

So the first TB skin test stimulates boosts the immune system, which then reacts strongly to the second skin test. Infection with bacteria similar to Mycobacterium tuberculosis. This may also cause a first TB skin test to boost the immune system, allowing it to react strongly to a second test, even though a new TB infection has not occurred.

Other tests, such as a chest X-ray, sputum cytology, and sputum culture, may be done to confirm an active TB infection when a skin test is positive. A person who has a positive skin test or chest X-ray, but no TB symptoms, is usually thought to have a TB infection that cannot be passed to others latent TB.

Chest X-Ray Sputum Cytology Sputum Culture Among hospital workers or others who have periodic skin tests, a second test done within a few weeks of a negative test may be positive, even though the person was not infected between the two tests.

These results called the booster effect may indicate a TB infection that occurred a long time ago or a previous BCG vaccination. No more tests are needed for a person with a negative tuberculin skin test who has no symptoms of active infection and no history of being exposed to TB. Some people do not react to a tuberculin skin test even if they have tuberculosis. In these cases, other skin tests may be done.

If there is a skin reaction, then the tuberculin skin test is probably correct. A small amount of purified protein — taken from dead TB bacteria — is injected under the top layer of the skin, on the forearm. A small blister will appear at the site, which will disappear within 20 minutes. There may also be a small amount of blood at the needle site. A small lump may form at the injection site over the next few days and you will need to return to your doctor or nurse 3 days later to have this assessed.

The size of your lump — measured in millimetres — will indicate whether or not you have a latent TB infection. If the lump is below a certain size, the result of the test is negative. Usually this means that you have not been infected with TB bacteria. However, if your contact with TB was very recent, you may need to have the test repeated in 8 to 12 weeks. A false negative can occur if you are unwell, have a weak immune system, or have had a recent live vaccination.

If the lump is above a certain size, the result of the test is positive. It means that you may have been infected with the TB bacteria. It does not mean you have TB disease active TB. When you are infected with TB bacteria you are not infectious and you cannot pass the bacteria onto other people. You are not sick but, at some stage in the future, you may develop TB disease. If you are told your TST is positive you may be asked to see a doctor for review. You will be given your result when you have the reading done.