Hiba Saleemalmost 3 years ago

Classification of the PPD (Tuberculin Skin Test) Reaction

The purified protein derivative (PPD) skin testing for tuberculosis is only indicated in those who have latent TB. It is not useful in symptomatic patients or those who have an abnormal chest x-ray. It involves injecting a small amount the PPD, tuberculin, into the skin of the forearm. It's also called the tuberculin skin test (TST). The induration developed on the skin is then measured after 72 hours. The criteria for considering the test to be positive is described in the picture above.