Two-Stage Tuberculin (PPD) Skin Testing in Individuals With Human Immunodeficiency Virus (HIV) Infection

The accuracy of skin testing to detect Mycobacterium tuberculosis (MTb) infection is dependent upon the host's ability to mount a delayed-type hypersensitivity (DTH) reaction; however, the DTH response may be impaired or absent in patients with impaired cell-mediated immunity, a classic characteristic of HIV infection. Patients in whom immunity is diminished, but not absent, may test negative the first time a purified protein derivative skin test for MTb is administered, but if the same skin test is repeated, a positive DTH response may then be elicited. This occurrence is known as the "booster" phenomenon. Patients who have had a negative purified protein derivative (PPD) skin test for M. tuberculosis within 7-28 days prior to study entry will receive a second PPD test by the Mantoux method (5 TU intradermally to the volar aspect of the forearm). Skin tests will be read 48-72 hours after application. Patients with a positive skin test (defined as an induration, or small hard knot, of 5 mm or greater forming beneath the skin) will be referred to their primary physicians for further evaluation.