Purified protein derivative standard; TB skin test; Tuberculin skin test
What the risks are
There is a very small risk of severe redness and swelling of the arm in people who have had a previous positive PPD test and who have the test again. There also have been a few cases of this reaction in people who have not been tested before.
Special considerations
A positive skin test does not necessarily mean that a person has active tuberculosis. More tests will be done to check whether there is active disease.
Many people who were born outside the United States may have had a vaccine called "BCG," which can lead to a false-positive test result. However, many experts believe that a past BCG vaccination should not change the PPD result when the test is done 15 years after the vaccination.
Previous Section
