PPD skin test

  • Definition

    The PPD skin test is a method used to diagnose tuberculosis (TB). PPD stands for purified protein derivative.

    Alternative Names

    Purified protein derivative standard; TB skin test; Tuberculin skin test; Mantoux test

    How the test is performed

    The test site (usually the forearm) is cleansed with rubbing alcohol. The PPD extract is then injected under the top layer of skin, causing a welt to form on the skin. This welt usually goes away in a few hours.

    The reaction will take 48 - 72 hours to develop. You must return to your health care provider at that time to have the area checked. This check will determine whether you have had a significant reaction to the PPD test. The reaction is measured in millimeters of firm swelling (induration), not redness, at the site of infection.

    How to prepare for the test

    There is no special preparation for this test.

    Tell your health care provider if you have ever had a positive PPD skin test. If so, you should not have a repeat PPD test, except under unusual circumstances.

    Tell your doctor if you have a medical condition or if you take certain drugs, such as steroids, that can affect your immune system. These situations may lead to inaccurate test results.

    How the test will feel

    You will feel a brief sting as a needle is inserted just below the skin surface.

    Why the test is performed

    The PPD test is done to find out if you have been infected with Mycobacterium tuberculosis, the bacteria that cause TB.