What Does a Positive TB Skin Test Mean?

A positive TB or tuberculin skin test means that the individual tested was infected with the TB bacteria. The TB skin test, however, will not say if the individual has a latent TB infection or has the disease. Additional tests such as a chest x-ray or a sputum examination will be required to confirm whether or not the person is infected with TB bacteria or is suffering from TB disease.

The TB skin test is also called the Mantoux test, named after the French physician, Charles Mantoux, who created the test in 1907. Endorsed by the Center for Disease Control and Prevention (CDC) and the American Thoracic Society, the TB skin test is one of the major TB screening tools used around the world.

The test is conducted by injecting a small amount of fluid, called “tuberculin,” intradermally into the inner lower part of the arm. The injection site will be examined after 48 to 72 hours by a medical professional, and measurements will be taken to see how much the skin around the injection site has raised to determine a positive or negative result.

The CDC recommends the TB skin test for:

  • People who have spent some time with anyone who has TB disease.
  • People who have spent time with anyone who is infected with HIV virus or a medical condition that weakens the immune system response.
  • People who show signs and symptoms of TB disease.
  • People who have traveled to a country where TB disease is common.
  • Healthcare workers who care for TB patients.
  • People who use recreational drugs.