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.
To quantitate in an HIV-infected population the percentage of patients demonstrating the booster phenomenon (attainment of a positive response to a second tuberculin purified protein derivative skin test when the first skin test was negative); to determine the relationship between the booster phenomenon and CD4-positive lymphocyte cell counts; to detect any relationship between the booster phenomenon and HIV exposure category.~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.