PPD skin test

Alternative names:

purified protein derivative

Normal values:

A negative reaction or no inflammation at the test site is normal.

What abnormal results mean:

The significance of the reaction depends on the circumstances and the size of the reaction on the skin. The reaction is measured in millimeters of induration (hard swelling) at the site. For example, if you have relatives who have tuberculosis, a small reaction could be important. How long the reaction lasts is as important as the size.