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Copyright © 2001 National Academy of Sciences
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Tuberculosis is a treatable, communicable disease that has two general states: latent infection and active disease. With few exceptions, only those who develop active tuberculosis in the lungs or larynx can infect others, usually by coughing, sneezing, or otherwise expelling tiny infectious particles that someone else inhales.
Although tuberculosis is still a major killer in poor countries, 50 years of effective drug treatment has greatly reduced the toll that the disease takes in developed countries. Nonetheless, after more than 30 years of declines in reported tuberculosis cases and deaths, the mid-1980s and early 1990s saw a reversal of that trend in the United States. This resurgence of tuberculosis, which included several outbreaks of the disease among hospital patients and workers, prompted considerable concern among health care workers, administrators, public health professionals, and policymakers. Renewed public and private efforts to control the disease followed. These efforts included the initiation of a rulemaking process by the federal Occupational Safety and Health Administration (OSHA) that led, in 1997, to the publication of proposed regulations on occupational tuberculosis.
In November 1999, the U.S.Congress requested that the National Academy of Sciences undertake a short-term study to examine the risk of tuberculosis among health care workers and the possible effects of federal guidelines and regulations intended to protect workers from this risk. Between April and September 2000, a committee of the Institute of Medicine (IOM), the health policy arm of the Academy, investigated three questions:
1. Are health care and selected other categories of workers at a greater risk of infection, disease, or mortality due to tuberculosis than others in the communities in which they reside?
2. What is known about the implementation and effects of the 1994 Centers for Disease Control and Prevention (CDC) guidelines for the prevention of tuberculosis in health care facilities?
3. What will be the likely effects on rates of tuberculosis infection, disease, and mortality of an anticipated OSHA standard to protect workers from occupational exposure to tuberculosis?
The committee's charge from Congress for this limited study did not include the development of recommendations for regulatory policy. It also did not include an evaluation of the costs or cost-effectiveness of implementing a standard.
Overall, the committee concludes that tuberculosis remains a threat to some health care, correctional facility, and other workers in the United States. Although the risk has been decreasing in recent years, vigilance is still needed within hospitals, prisons, and similar workplaces, as well as in the community at large. Fortunately, tuberculosis control measures recommended by the CDC in response to tuberculosis outbreaks in health care facilities appear to have been effective. Available evidence suggests that where tuberculosis is uncommon or where basic infection control measures are in place, the occupational risk to health care workers of tuberculosis now approaches community levels, which have been declining. The primary risk to workers today comes from patients, inmates, or others with unsuspected and undiagnosed infectious tuberculosis.
The committee also concludes that an OSHA standard on occupational tuberculosis can have a positive effect if it meets three basic conditions: (1) it is consistent with tuberculosis control measures that appear to be effective, (2) it increases or sustains the level of compliance with those measures, and (3) it allows appropriate flexibility for organizations to adopt tuberculosis control measures appropriate to the level of risk facing workers. The committee expects that a standard will meet the first two conditions by sustaining or increasing the use of effective tuberculosis control measures. The committee is, however, concerned that if a final OSHA standard follows the 1997 proposed rule, it may not meet the third condition of allowing reasonable flexibility to adopt measures appropriate to the level of risk.
CDC GUIDELINES AND THE PROPOSED OSHA RULE
1994 CDC Guidelines
In 1994, CDC published its most extensive guidelines for preventing the transmission of tuberculosis in health care facilities (including health care units in prisons, jails, and certain other settings). The guidelines present a three-level hierarchy of tuberculosis control recommendations comprising
1. administrative controls (in particular, protocols for early identification, isolation, and treatment of individuals with infectious tuberculosis),
2. engineering controls (in particular, negative-pressure ventilation of isolation rooms for patients with infectious tuberculosis), and
3. personal respiratory protection (primarily use of specially designed facemasks to prevent inhalation of infectious particles).
The CDC guidelines, which followed statements issued in 1982 and 1990, also set forth a risk assessment process that defines five categories of facilities (or areas of facilities) based on the risk of tuberculosis transmission. The guidelines recommend fewer tuberculosis control measures for the facilities in the "minimal" and "very low" risk categories. The risk assessment process for a facility covers the profile of tuberculosis in the community, the numbers of tuberculosis patients examined or treated in different areas of the facility, and the tuberculin skin test conversion rates for workers in different areas of the facility or in different job categories. The process also takes into account evidence of person-to-person transmission of tuberculosis resulting in active disease as well as information from medical record reviews or workplace observations that suggests possible problems in tuberculosis control measures. In the summer of 2000, CDC began a reassessment of its guidelines for health care facilities, and the results are expected in mid-2002.
1997 Proposed OSHA Rule
When the committee began work in April 2000, OSHA expected to publish the final standard on occupational tuberculosis in July. Subsequently, OSHA indicated that publication would likely occur by the end of the year 2000, which would follow the committee's final meeting in September 2000. Thus, the committee had to undertake its analyses without knowing the content of the final regulations. It is possible that the new Administration will not issue any final standard.
By law, OSHA can directly regulate only private employers and, with certain restrictions, federal agencies. Through agreements with states that choose to participate, OSHA regulations may also be applied to employees of state and local governments. About half the states have entered into such agreements.
In its 1997 proposed rule on occupational tuberculosis, OSHA followed the 1994 CDC guidelines in most respects. Also, OSHA concluded that the CDC guidelines in their original form were not specific and directive enough to be adopted directly as a regulatory standard. The proposed rule, therefore, differs from the CDC guidelines in certain ways. First, the proposed rule is written to be enforced and, therefore, tends to be more specific and directive than the CDC guidelines. Second, it would cover a broader group of employers and employees. Third, it is intended to protect employees and not, for example, patients, prisoners, or visitors. Fourth, it sets forth very restrictive criteria for defining "low-risk" employers that would not be expected to implement all the rule's requirements.
The 1997 proposed OSHA rule defines a category of employers that would be exempt from some of its requirements, but the qualifying criteria are narrower than those set forth in the 1994 CDC guidelines. Specifically, a facility must neither admit nor provide medical services to individuals with suspected or confirmed tuberculosis, it must have had no confirmed cases of infectious tuberculosis during the previous 12 months, and it must be located in a county that has had no confirmed cases of infectious tuberculosis during 1 of the previous 2 years and less than six cases during the other year. Even if a facility had admitted no tuberculosis patients in the preceding 12 months, had no tuberculosis cases in its service area, and had a policy of referring those with diagnosed or suspected tuberculosis, that facility could not qualify for this "lower risk" category if the surrounding county had reported one case of tuberculosis in each of the preceding 2 years.
ASSESSMENT AND CONCLUSIONS
Context: Changing Tuberculosis Case Rates and Community and Workplace Responses
The committee's conclusions need to be understood in context. This context includes the changing epidemiology of the disease over the past two decades, the evolution of community and institutional responses to the perceived threat of tuberculosis, and the persistence of geographic variations in community levels of tuberculosis.
Resurgent Tuberculosis, 1985-1992
Between 1985 and 1992, reported cases of tuberculosis increased by 20 percent, from 22,201 in 1985 to 26,673 in 1992. The case rate per 100,000 population increased by more than 12 percent, from 9.3 in 1985 to 10.5 in 1992. The number of deaths rose from 1,752 in 1985 to 1,970 in 1989. In the early 1980s, about 0.5 percent of new tuberculosis cases were resistant to the two major antituberculosis drugs, isoniazid and rifampin. By 1991, that figure had risen to 3.5 percent.
In addition, during the late 1980s and early 1990s, several U.S. hospitals experienced outbreaks of tuberculosis that affected both patients and employees. Some outbreaks involved a particularly lethal combination of multidrug-resistant disease and people with suppressed immune systems, most often related to HIV infection. Outbreaks also occurred in prisons and other workplaces serving people at increased risk of tuberculosis.
Lack of Preparation
In general, public health departments, health care facilities, prisons, and similar organizations were not prepared to cope with the resurgence of tuberculosis in the mid-1980s. After years of effective treatment and declining case rates, tuberculosis control measures were not a priority in either the community or the workplace. The HIV/AIDS epidemic and its interaction with tuberculosis were not well documented or understood. Similarly, the threat of multidrug-resistant tuberculosis resulting from incomplete treatment of the disease had yet to be clearly appreciated. Workplace outbreaks of tuberculosis were often associated with lapses in infection control measures.
The resurgence of tuberculosis in communities and the outbreaks of the disease in workplaces prompted a range of public and private responses. Congress revived federal funding for tuberculosis control programs, which had virtually disappeared in the 1970s. States and some cities and counties also began to rebuild programs that had been neglected or dismantled. These programs focused on groups at increased risk of tuberculosis such as people with HIV infection or AIDS, and they emphasized directly observed therapy for individuals with active tuberculosis. Hospitals, prisons, and perhaps other institutions, especially those affected by outbreaks and those located in high-risk areas, improved their infection control programs.
Guidelines and Regulations
In 1990, CDC issued new guidelines for tuberculosis control measures in health care facilities. In 1993, in response to calls from health care and other workers, OSHA began to enforce some tuberculosis control measures under its general powers to protect worker safety and under other regulations related to airborne hazards. In 1994, the agency began a formal rulemaking process to develop specific regulations on occupational tuberculosis. Also in 1994, CDC issued a major revision of its 1990 guidelines for the prevention of transmission of tuberculosis in health care facilities. OSHA published a proposed rule on occupational tuberculosis in 1997 and solicited comments on the rule in 1998 and again in 1999. In addition, some state licensure agencies and private accrediting organizations required tuberculosis control measures.
Decreasing Rates of Disease
The epidemiology of tuberculosis has changed substantially since the early 1990s. In 1993, the trend of increasing tuberculosis case rates began to reverse, and declines have now been recorded for 7 successive years. Tuberculosis case rates reached new lows in 1999, when CDC reported a rate of 6.4 per 100,000 population, a 35 percent drop since 1992. Cases of multidrug-resistant disease have also decreased; in 1999, they accounted for just 1.2 percent of cases. In general, fewer cases of tuberculosis and less multidrug-resistant disease mean less risk for nurses, doctors, correctional officers, and others who work for organizations that serve people who have tuberculosis or who are at increased risk of the disease.
Continuing Geographic Variation
Despite the general decline in tuberculosis rates in recent years, a marked geographic variation in tuberculosis case rates persists, which means that workers in different areas face different potential risks. Among metropolitan statistical areas, 1999 case rates varied from 1.3 per 100,000 population in Omaha to 17.7 per 100,000 in New York City and 18.2 per 100,000 in San Francisco. Between 1994 and 1998, six states-California, Florida, Illinois, New Jersey, New York, and Texas-accounted for 57 percent of tuberculosis cases but had just under 40 percent of the U.S. population. These states also account for a large proportion of people with risk factors for the disease, notably, HIV infection and immigration from countries with a high prevalence of tuberculosis. More than 40 percent of tuberculosis cases reported in the United States in 1999 involved people born in other countries, primarily Mexico, the Philippines, and Vietnam.
One problem facing the IOM committee as well as CDC and OSHA was the lack of prospective, controlled studies documenting the effectiveness of specific protective measures in preventing the transmission of tuberculosis in the workplace. Most studies of these protective measures are retrospective or observational, and they are inconsistent in their methods and reporting. The studies typically involve organizations-mainly hospitals-that experienced tuberculosis outbreaks and then implemented multiple control measures in a fairly short period of time.
No national data on occupational risk of tuberculosis infection are available, and data from surveys, outbreak studies, and other sources are subject to various biases. Data are especially sparse for workplaces other than hospitals. This lack of information is troubling because many of these facilities serve people at increased risk of active tuberculosis-including people who are unemployed, homeless, or poor; people with human immunodeficiency virus (HIV) infection or AIDS or substance abuse problems; and recent immigrants from countries with high rates of tuberculosis. These other workplaces may lack the resources and expertise available to hospitals to assess the risk to workers and undertake appropriate precautions. External oversight may also be more limited.
After reviewing scientific and other literature, considering discussions held during the committee's public meetings, and drawing on its members' experience and judgment, the committee reached several conclusions in response to the questions posed to it. Again, the committee's charge and resources did not provide for consideration of policy options and recommendations.
Question 1: Are health care and selected other categories of workers at greater risk of infection, disease, or mortality due to tuberculosis than others in the community in which they reside? (Continues...)
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|Risks to Health Care and Other Workers||15|
|Overview of Report||16|
|Responses to Resurgent Tuberculosis||17|
|The Broader Public Health Context: Eliminating Tuberculosis in the United States and Worldwide||21|
|2||Basics of Tuberculosis||24|
|Transmission and Development of Latent Tuberculosis Infection and Active Tuberculosis||25|
|Detection and Treatment of Latent Tuberculosis Infection||28|
|Diagnosis and Treatment of Active Tuberculosis||37|
|3||Occupational Safety and Health Regulation in Context||43|
|Strategies for Reducing Workplace Hazards||43|
|The Occupational Safety and Health Act of 1970 and Its Administration||45|
|4||Comparison of CDC Guidelines and Proposed OSHA Rule||56|
|CDC Guidelines on Preventing Transmission of Tuberculosis in Health Care Facilities||57|
|Proposed OSHA Rule on Occupational Exposure to Tuberculosis||59|
|Comparison of Guidelines and Proposed Rule: Administrative Controls||63|
|Comparison of Guidelines and Proposed Rule: Engineering Controls||74|
|Comparison of Guidelines and Proposed Rule: Personal Respiratory Protections||76|
|5||Occupational Risk of Tuberculosis||81|
|Concepts and Definitions||82|
|Historical Perspectives on the Occupational Risk of Tuberculosis||85|
|More Recent Information on the Community and Occupational Risk of Tuberculosis||86|
|6||Implementation and Effects of CDC Guidelines||108|
|Implementation of Tuberculosis Control Guidelines||109|
|Effects of Implementing Tuberculosis Control Measures||122|
|7||Regulation and the Future of Tuberculosis in the Workplace||137|
|Potential Effects of an OSHA Standard on Occupational Tuberculosis||138|
|The Workplace and the Community||154|
|App. A: Study Origins and Activities||173|
|App. B||The Tuberculin Skin Test||179|
|App. C||The Occupational Tuberculosis Risk of Health Care Workers||189|
|App. D||Effects of CDC Guidelines on Tuberculosis Control in Health Care Facilities||230|
|App. E||OSHA in a Health Care Context||271|
|App. F||Respiratory Protection and Control of Tuberculosis in Health Care and Other Facilities||293|
|App. G||Recommendations of the Institute of Medicine Committee on Eliminating Tuberculosis in the United States||309|
|App. H: Committee Biographies||314|