Overview
The purified protein derivative is an antigen (a substance that stimulates the immune system to eliminate or fight foreign substances in the body), which is injected under the skin in the forearm. After 48 to 72 hours the injection site is evaluated by a physician. This skin test helps determine if a person has ever been infected by the microorganism that causes tuberculosis.
Review Date 12/31/2023
Updated by: Jatin M. Vyas, MD, PhD, Roy and Diana Vagelos Professor in Medicine, Columbia University Vagelos College of Physicians and Surgeons, Division of Infectious Diseases, Department of Medicine, New York, NY. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.