When Ppd Test Is Positive?

The most commonly used skin test to check for TB is the PPD — purified protein derivative. If you have a positive PPD, it means you have been exposed to a person who has tuberculosis and you are now infected with the bacteria (mycobacterium tuberculosis) that causes the disease.

How long before TB test shows positive?

In a person who is newly infected, the skin test usually becomes positive within 4 to 10 weeks after exposure to the person who is ill with TB. (See "Approach to diagnosis of latent tuberculosis infection (tuberculosis screening) in adults".)

Will I always test positive for PPD?

Once you have a positive TB skin test you will always have a positive TB skin test, even if you complete treatment. Ask your doctor for a written record of your positive skin test result. This will be helpful if you are asked to have another TB skin test in the future.