TUBERCULOSIS INFECTION AMONG STAFF AT A CANADIAN COMMUNITY-HOSPITAL

OBJECTIVE: To determine risks for tuberculin skin-test conversion amon g employees of a community hospital in Ontario, Canada. DESIGN: Cohort morbidity study. SETTING: Of 14 metropolitan Toronto area hospitals s urveyed for data on tuberculin skin-test conversions, only one provide d tuberculosis (TB) test data on all employees. Between 1991 and June 1994, 24 patients were treated at this hospital for pulmonary TB. POPU LATION STUDIED: The population at risk included those on staff from Ja nuary 1991 through December 1993 who previously were skin-test negativ e; they were followed until the end of June 1994. Exposure was estimat ed (a) based on ranking departments according to an estimate of the nu mber of hours of direct patient contact during a typical day, and (b) based on location of sputum-positive patients. OUTCOME MEASURE: Risks of skin-test conversion among hospital employees with documented prior negative skin tests. MAIN RESULTS: A total. of 809 skin-test negative employees were followed for 2,084 person-years; 18 employees with ski n-test conversions were identified. The overall conversion rate was 0. 9% per year (0.86 per 100 person-years). After excluding two conversio ns attributed to contact with coworkers, the relative risk of conversi on was 4.5 (5.5 after adjusting for age and gender) among those in the highest exposure category (greater than or equal to 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-posi tive patients were treated, 2.4% converted; the risk of conversion was over six times greater than among those working on wards with no TB p atients or in departments with no patient contact, of whom 0.4% conver ted. Among the emergency room staff, the department in which the great est number of sputum-positive patients were treated, at least 5% of st aff converted. In those instances in which conversions were associated with exposure to a specific TB patient, the involved patients had bee n in the hospital for at least 4 days prior to being isolated. CONCLUS IONS: These results indicate that even in a hospital with few admissio ns due to tuberculosis, skin-test conversions associated with occupati onal exposure may occur.