Hospital ventilation and risk for tuberculous infection in Canadian health care workers

Background: The risk for and determinants of transmission of tuberculosis in hospitals caring for moderate numbers of patients with tuberculosis remain uncertain. Objective: To study the association of tuberculin conversion among health care workers with ventilation of patient care areas. Design: Cross-sectional observational survey. Setting: 17 acute-care community or university hospitals. Participants: All personnel who worked at least 2 days per week in the respiratory and physiotherapy departments or in selected nursing units. Measurements: Participating workers underwent tuberculin skin testing and completed self-administered questionnaires. Previous tuberculin tests and bacille Calmette-Guerin vaccinations were verified. Records of patients with tuberculosis who were hospitalized in the 3 years preceding the study were reviewed. Air exchanges per hour in patient care areas were measured by using a tracer gas technique. Multivariate proportional hazards regression was used to estimate the effect of occupational factors on documented tuberculin conversion, after adjustment for nonoccupational factors, among participants with at least one previous negative result on tuberculin skin testing. Results: Tuberculin conversion was associated with ventilation of general or nonisolation patient rooms of less than 2 air exchanges per hour (adjusted hazard ratio, 3.4 [95% Cl, 2.1 to 5.8]); with work in moderate- to high-risk hospitals (adjusted hazard ratio, 2.2 [Cl, 1.3 to 3.5]); and with work in the nursing (adjusted hazard ratio, 4.3 [Cl, 2.7 to 6.91), respiratory therapy (adjusted hazard ratio, 6.1 [Cl, 3.1 to 12.0]), and physiotherapy (adjusted hazard ratio, 3.3 [Cl, 1.5 to 74) departments or housekeeping (adjusted hazard ratio, 4.2 [Cl, 2.3 to 7.6]). Conversion was not associated with inadequate ventilation of respiratory isolation rooms (adjusted hazard ratio, 1.0 [Cl, 0.8 to 1.3). Conclusion: Tuberculin conversion among health care workers was strongly associated with inadequate ventilation in general patient rooms and with type and duration of work, but not with ventilation of respiratory isolation rooms.