Discrepancies in tuberculin skin test results with two commercial products in a population of intravenous drug users.

Screening for tuberculosis (using the Mantoux test) and human immunodeficiency virus (HIV) was conducted among intravenous drug users (IVDUs) recruited from a San Francisco Bay Area neighborhood. Of 178 IVDUs skin-tested with one commercial purified protein derivative (PPD) preparation, a reaction of > or = 5 mm of induration occurred in 62 (47%) of 133 HIV-negative and 13 (29%) of 45 HIV-positive IVDUs (P = .037). Forty-two IVDUs with an initial PPD reaction > or = 5 mm were retested with a second commercial preparation; 11 (26%) had no reaction (0 mm) on retesting. These 11 were 5 (56%) of 9 HIV-positive and 6 (18%) of 33 HIV-negative persons (P = .038). These discrepancies may be unique to specific lots of product or may reflect more general differences. A degree of caution in evaluating unexpected tuberculin skin test results may be indicated. Response to different tuberculin products by HIV status should be further evaluated.