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PPD skin test - Overview

Alternative Names

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

Definition of PPD skin test:

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

How the test is performed:

The test site (usually the forearm) is cleansed. The PPD extract is then injected under the top layer of skin, causing a blister to form on the skin.

The reaction will take 48 - 72 hours to develop. You must return to your health care provider within that time to have the area checked. This will determine whether you have had a significant reaction to the PPD test. A reaction is measured in millimeters of hard swelling (induration) at the site.

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.

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 test is done to find out if you have been infected with tuberculosis.

Tuberculosis in the kidney

Tuberculosis in the lung

Positive PPD skin test

PPD skin test

Reviewed last on: 9/28/2008
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Jatin M. Vyas, PhD, MD, Instructor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

References

Centers for Disease Control and Prevention. Questions and answers about TB. 2007. Accessed September 28, 2008.

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