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After Congress asked the Institute of Medicine (IOM) to address the much-debated area of tuberculosis (TB) regulations in health care, the IOM formed a study panel and focused its research around three critical questions. Here is a summary of the IOM’s answers to those questions, taken from its Jan. 16, 2001, report:
Question 1: Are health care and selected other categories of workers at greater risk of infection, disease, or mortality due to TB than others in the community in which they reside?
Answer: Through at least the 1950s, health care workers were at higher risk from TB than others in the community. Currently available data suggest where TB is uncommon or where basic infection control measures are in place, the occupational risk to health care workers of TB infection now approaches the level in their community of residence. TB risk in communities has been declining since 1993.
Overall, rates of active TB among health care workers are similar overall to those reported for other employed workers. Data do not allow comparisons of mortality risk, but health care workers and others with compromised immune function are at high risk of death if they contract multidrug-resistant disease.
The primary risk to health care, correctional, and other workers now comes from patients, inmates, or clients with unsuspected, undiagnosed infectious TB. Risk is influenced by the prevalence of TB in the community that the workplace serves and by the extent and type of worker’s contact with people who have infectious TB. The available data do not allow precise quantification of the risk to health care workers or conclusions about the historical or current risk to other categories of workers covered by the 1997 proposed Occupational Safety and Health Administration (OSHA) rule.
Question 2: What is known about the implementation and effects of the 1994 Centers for Disease and Control guidelines for the prevention of TB in health care facilities?
Answer: Data from surveys, facility inspections, and other sources indicate that institutional departures from recommended TB control policies and procedures were common, if not the norm, in the late 1980s and the early 1990s. By the mid-1990s, hospitals, and, less clearly, other health care organizations and correctional facilities began to take TB control measures more seriously. Implementation is probably most complete for administrative controls including procedures for promptly identifying, isolating, diagnosing, and adequately treating people with active TB.
For engineering controls, available data suggest that the rate of installation of negative-pressure isolation rooms has increased, but not all in-use rooms are assessed on a daily basis to ensure that they remain under negative pressure. Information about personal respiratory protection programs is very limited. It suggests that most hospitals have been providing some kind of protection and have been updating the equipment provided as new options, such as the N95 respirator, have been developed and certified.
Overall, the measures recommended by the CDC in 1994 and earlier to prevent the transmission of TB in health care facilities have contributed to ending hospital outbreaks of TB and preventing new ones. Studies of outbreaks as well as logic and biologic plausibility support the CDC’s stress on administrative controls, particularly the rigorous application of protocols for the prompt identification and isolation of people with signs and symptoms suspicious for infectious TB.
Studies of outbreaks and modeling exercises suggest that engineering controls also make a contribution in limiting the transmission of TB. Available information suggests that most of the benefit of control measures comes from administrative and engineering controls. Modeling studies 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.
Although control measures have helped to end workplace outbreaks of TB and prevent transmission of the disease, these measures cannot be expected to prevent all types of worker exposure to TB. In areas with moderate to high levels of TB, some worker exposure to patients with unsuspected infectious TB can be expected. Conscientious implementation of TB control measures does not guarantee that transmission will never occur, but it appears to reduce risk significantly, especially in high-prevalence areas.
Question 3: What will be the likely effects on rates of TB infection, disease, and mortality of an anticipated OSHA standard to protect workers from occupational exposure to TB?
Answer: Because the committee had to work without access to the final OSHA regulations on occupational TB, it could not be certain of whether or how the final standard would differ from the 1997 proposed rule or from the 1994 CDC guidelines.
Therefore, rather than concentrate narrowly on individual features of the proposed rule, the committee decided to consider more generally the conditions that would need to be met for a standard to have positive effects on TB infection, disease, or mortality. It identified three such conditions:
1. Implementation of workplace TB control measures as recommended by CDC and proposed by OSHA must contribute meaning-fully to the prevention of transmission of Mycobacterium tuberculosis in hospitals and other covered workplaces.
2. An OSHA standard must sustain or increase the level of adherence to workplace TB control measures, especially in high-risk institutions and communities.
3. An OSHA standard must allow reasonable adaptation of TB control measures to fit differences in the levels of risk facing workers.
Overall, the committee expects that the first of the conditions outlined above — that TB control measures are effective — will be met for hospitals and possibly correctional facilities. Insufficient information is available to assess the effectiveness of control measures in other workplaces.
The committee expects that the second condition also will be met; an OSHA standard will sustain or increase the level of compliance with mandated TB control measures. A standard is likely to motivate more organizational adherence to control measures than can be achieved by voluntary guidelines.
A standard also is likely to be clearer, more hazard-specific, and easier to use than the other legal strategies available to OSHA. In addition, by providing a firmer basis for OSHA enforcement actions, a standard also will put workers on stronger ground in identifying and challenging an employer’s inadequate implementation of mandated TB control measures.
The committee is concerned, however, that if an OSHA standard follows the 1997 proposed rule, it may not meet the third condition of allowing organizations reasonable flexibility to adopt TB control measures appropriate to the level of risk facing workers.
The 1997 proposed rule defines a category of employers that would be excused from some of the rule’s requirements, but the criteria defined are very narrow and would likely subject too many low-risk organizations to the rule’s full scope. In addition, as an indicator of TB risk in the community, the proposed rule would require use of county-level data to assess community risk, even though a facility’s service area might be quite different and have a much different incidence of TB.
To the extent that an OSHA standard inflexibly extends requirements to institutions that are at negligible risk of occupational transmission of M. tuberculosis, the standard is unlikely to benefit workers at the same time that it would impose significant costs and administrative burdens on covered organizations and absorb institutional resources that could be applied to other, potentially more beneficial uses.
The committee also concludes that OSHA’s 1997 estimates overstated the number of infections, cases of disease, and deaths due to TB that would be averted by adoption of the 1997 proposed rule. (The committee did not have access to OSHA’s recently revised estimates.) TB case rates are down substantially from 1994 and the earlier years used for the estimates, and implementation of community and workplace TB control measures appears to be considerably improved.
Recent data on TB infection are limited but indicate low levels of TB infection in health care facilities and suggest that exposure in the community is a significant factor in health care worker infections.
In addition, the agency’s estimates relied on assumptions about the progression of TB from infection to active disease and from disease to death that are widely used but inconsistent with available data and are unlikely to fit employed workers with reasonably good access to health care.