Tuberculosis infection among staff at a Canadian community hospital.

Abstract

To determine risks for tuberculin skin-test conversion among employees of a community hospital in Ontario, Canada. Cohort morbidity study. Of 14 metropolitan Toronto area hospitals surveyed for data on tuberculin skin-test conversions, only one provided tuberculosis (TB) test data on all employees. Between 1991 and June 1994, 24 patients were treated at this hospital for pulmonary TB. The population at risk included those on staff from January 1991 through December 1993 who previously were skin-test negative; they were followed until the end of June 1994. Exposure was estimated (a) based on ranking departments according to an estimate of the number of hours of direct patient contact during a typical day, and (b) based on location of sputum-positive patients. Risks of skin-test conversion among hospital employees with documented prior negative skin tests. A total of 809 skin-test negative employees were followed for 2,084 person-years; 18 employees with skin-test conversions were identified. The overall conversion rate was 0.9% per year (0.86 per 100 person-years). After excluding two conversions attributed to contact with coworkers, the relative risk of conversion was 4.5 (5.5 after adjusting for age and gender) among those in the highest exposure category (> or = 4 hours per day), compared to those in departments ranked as having the lowest exposure (< 2 hours per day). Among those working in wards in which sputum-positive patients were treated, 2.4% converted; the risk of conversion was over six times greater than among those working on wards with no TB patients or in departments with no patient contact, of whom 0.4% converted. Among the emergency room staff, the department in which the greatest number of sputum-positive patients were treated, at least 5% of staff converted. In those instances in which conversions were associated with exposure to a specific TB patient, the involved patients had been in the hospital for at least 4 days prior to being isolated. These results indicate that even in a hospital with few admissions due to tuberculosis, skin-test conversions associated with occupational exposure may occur (Infect Control Hosp Epidemiol 1996; 17:29-35).