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Hospital Ventilation and Tuberculosis in Canadian Health Care Workers
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What is the problem and what is known about it so far?
Tuberculosis is an infection that usually affects the lungs, but it can also affect other body organs. Tuberculosis spreads when a person with this lung infection coughs and releases tuberculosis bacteria into the air. When persons with tuberculosis are hospitalized, it is very important to use special precautions (masks and isolation rooms) to keep the infection from spreading to other patients and hospital workers. In the early 1990s, several outbreaks of tuberculosis in hospitals drew attention to this issue. New recommendations suggested strict infection control precautions, including special ventilation systems in hospitals. Reports suggest that these precautions have decreased the spread of tuberculosis in hospitals. However, none of these studies was able to examine the role of ventilation systems alone. Since these ventilation systems can be expensive and difficult to install, it would be useful to know how well they work.
Why did the researchers do this particular study?
To see whether exposure of hospital workers to tuberculosis is associated with the ventilation systems in place where they work.
Who was studied?
Health care workers who worked at least 2 days per week on selected wards of 17 community and teaching hospitals in Canada.
How was the study done?
The researchers asked the workers to undergo skin tests for tuberculosis and to complete a survey. The skin tests show whether a person has been exposed to tuberculosis. The researchers reviewed the records of all patients with tuberculosis who were hospitalized at each hospital during the previous 3 years. The researchers also did special tests of ventilation that measured air flow at various locations in the hospital. They then looked for associations between hospital ventilation and positive test results for tuberculosis in hospital workers.
What did the researchers find?
Positive test results for tuberculosis were associated with poor ventilation in general patient rooms. Other factors related to testing positive for tuberculosis were working in hospitals that had more patients with tuberculosis and having certain types of hospital jobs (nursing, respiratory therapy, physical therapy, or housekeeping). However, positive test results for tuberculosis were not associated with the ventilation in isolation rooms. This is probably because hospital workers usually wear masks when they enter isolation rooms.
What were the limitations of the study?
The study involved only 17 hospitals in Canada. The results might not apply to hospitals that see different numbers of patients with tuberculosis or have different infection control procedures.
What are the implications of the study?
Proper ventilation systems seem to be important in preventing the spread of tuberculosis in hospitals.
Article and Author Information
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The summary below is from the full report titled “Hospital Ventilation and Risk for Tuberculous Infection in Canadian Health Care Workers.” It is in the 21 November 2000 issue of Annals of Internal Medicine (volume 133, pages 779-789). The authors are D Menzies, A Fanning, L Yuan, JM FitzGerald, and the Canadian Collaborative Group in Nosocomial Transmission of TB.
- Copyright ©2004 by the American College of Physicians
