they suggest the need for some caution in accepting survey responses as conclusive. Departures from guidelines occur at both the institutional level (e.g., provision of respirators and installation of negative-pressure isolation rooms) and the individual level (e.g., use of respirators and closing doors of isolation rooms). Whether less than total compliance makes a practical difference in preventing workplace transmission of tuberculosis is a separate question.
The caveats cited for implementation also apply to the following conclusions about the effects of tuberculosis control measures. In addition, the committee could not readily disentangle the effects of the CDC guidelines from environmental influences including the effects of community public health measures, regulatory actions by OSHA and others, and the changing epidemiology of the disease. Furthermore, because control measures were often introduced simultaneously or close in time, the relative contribution of individual measures is difficult to distinguish. Finally, the committee could reach no conclusions about what level of compliance with different measures might be sufficient to prevent transmission of M. tuberculosis under different workplace conditions.
Again, the conclusions presented below apply primarily to hospitals. The picture for other workplaces is less clear.
Overall, the measures recommended by CDC for prevention of the transmission of tuberculosis in health care facilities have contributed to the ending of outbreaks of tuberculosis and the prevention of new outbreaks. This conclusion rests primarily on several outbreak reports and on information from institutions that did not report outbreaks but reduced skin test conversion rates after implementing control measures. Although each report has its limitations, taken together they show consistent results.
The hierarchy of control measures recommended by CDC is supported by studies of tuberculosis outbreaks in hospitals as well as by logic and biologic plausibility. Outbreak studies support CDC’s stress on administrative controls, in particular, application of protocols to reduce opportunities for worker or patient exposure to M. tuberculosis through prompt identification and isolation of people with signs and symptoms suspicious for infectious tuberculosis. Outbreak studies and modeling exercises suggest that engineering controls also make a contribution in limiting the transmission of tuberculosis. Although outbreak studies suggest that most of the benefit of control measures comes from administrative and engineering controls, modeling exercises support the tailoring of personal respiratory protections to the level of risk faced by workers—that is, more stringent protection for those in high-risk situations and less stringent measures for others.