Risk of Tuberculin Skin Test Conversion among Health Care Workers: Occupational versus Community Exposure and Infection

A prospective observational cohort study to assess rates of and risk factors for tuberculin skin test (TST) conversion among health care workers (HCWs) was conducted at an urban hospital located in a high tuberculosis-incidence area in 1994-1998. All hospital employees undergoing required testing every 6 months were included. A total of 69 (1.2%) of 5773 susceptible employees had a documented TST conversion (overall rate, 0.38 per 100 person-years worked). No significant difference existed in conversion rates among employees with frequent, limited, or no patient contact. HCWs with a TST conversion lived in zip codes with higher tuberculosis case rates (P ≤.05). In multivariate analysis, TST conversion was associated with history of bacille Calmette-Guerin vaccination (relative risk [RR], 11.63), annual salary <$20,000 (RR, 3.67), and increasing age. In the setting of an effective tuberculosis infection-control program, TST conversion rates were low, and risk of conversion among HCWs was associated most strongly with nonoccupational factors.