These guidelines were drafted by the American College of Occupational and Environmental Medicine's (ACOEM's) Occupational and Environmental Lung Disorders Committee; the lead author was Lawrence W. Raymond, MD. At the time of the guidelines' preparation, the Committee consisted of James E. Lockey, MD, Chairman; Henry Velez, MD, Associate Chairman; Arch I. Carson, MD; Clayton T. Cowl, MD; George L. Delclos, MD; Jordan N. Fink, MD; Brett J. Gerstenhaber, MD; Philip I. Harber, MD; Michael G. Holthouser, MD; Edward P. Horvath, Jr., MD; Athena T. Jolly, MD; Shadrach H. Jones IV, MD; Gary G. Knackmuhs, MD; Hilton C. Lewinsohn, MB; Larry A. Lindesmith, MD; Thomas N. Markham, MD; Lawrence W. Raymond, MD; David M. Rosenberg, MD; David Sherson, MD; Dorsett D. Smith, MD; and Mary Townsend, PhD. These guidelines were approved by the ACOEM Board of Directors on January 31, 1998.
The resurgence in cases of active pulmonary tuberculosis (TB) and the emergence of drug-resistant strains of TB have increased the risk that health care workers (HCWs) may acquire serious TB infections which may not respond to usual therapy. Multiple steps are needed to reduce this risk. These include updated training of HCWs to maintain awareness of potential risks of TB; optimizing the design, ventilation, and patient flow in clinical spaces; periodic tuberculin testing of HCWs; appropriate use of effective respiratory protection; active infection control procedures; and periodic updating of written TB control plans.1
ACOEM fully supports implementation of the Centers for Disease Control and Prevention (CDC) Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care Facilities, 1994.2,3 In particular, the College endorses the use of individual risk assessments for each clinical facility and its specific components, with review of the institution's TB-control program at appropriate intervals, in accordance with its case experience. The use of two-step tuberculin testing of newly hired HCWs (who have no documentation of a negative purified protein derivative (PPD) test result in the previous 12 months) can avoid pseudoconversions (positive tuberculin reactions due to anamnestic responses, rather than to recent workplace infections). The use of NIOSH-approved powered air purifying respirators (PAPR) or particulate filter respirators (N-95) will enhance protection for HCWs engaged in high-risk procedures such as bronchoscopy and other airway instrumentation, endoscopy, dental procedures, and sputum induction.3 Appropriate fit testing and medical-certification procedures consistent with the Occupational Safety and Health Administration (OSHA) 1910.139 Guidelines should be implemented. HCWs who are HIV-positive may need to be exempted from these and other TB-risk activities. The employer should make every attempt to honor requests for voluntary reassignment. All HCWs who could potentially care for or have airborne exposure from patients with active TB should have tuberculin testing every 3 to 12 months, depending on the risk assessment. HCWs with unprotected close contact with a patient with active TB should be retested as soon as possible (new "baseline") and, if negative, again 12 weeks later.
Tuberculosis is a highly communicable disease. Its spread is enhanced by the way TB organisms destroy lung tissue that they infect, often giving rise to cavities containing infected secretions. These secretions stimulate cough, which can help transmit the infection to other parts of the lung, as well as to other persons. Infective droplet nuclei may also be produced by sneezing, singing, or talking. Laryngeal TB is highly infectious and may be more difficult to diagnose and present without coughing. TB organisms tend to remain airborne after being coughed or exhaled into the surrounding air, often creating clusters of infection among exposed individuals in the patient's dwelling, workplace, aircraft or other transport vehicles, and social settings.
The risk of spread of TB from a given source case is related to the organism load in expectorated sputum or exhaled air and to how well those organisms are cleared from the air thus contaminated. This baseline risk level can be modified by the following measures:
- Prompt masking of persons suspected of having active TB and their isolation into a room under negative pressure.
- Appropriate and approved respiratory protection worn by potentially exposed HCWs.
- Prompt diagnosis and treatment of patients with active TB with regimens appropriate to community patterns of microbial resistance.
A high index of suspicion for TB can limit its spread to HCWs, and all health care and clerical workers with initial patient contact should be periodically trained to recognize the symptoms and signs of tuberculosis and to initiate protection protocols.
Recent Epidemiology of TB
By the early 1980s, hopes were high that TB would be eradicated in the United States by 2010.4 Even in high-prevalence areas such as East Africa, multi-drug, short-course treatment regimens had achieved tremendous success, both in far-advanced and less serious cases. For several reasons, however, the optimism was short-lived. A large number of immigrants with unrecognized TB arrived in the US during the 1980s.5 Cutbacks in funding for TB surveillance allowed such cases and domestic ones to give rise to many additional infections among close contacts because of crowding and other adverse socioeconomic conditions. The emerging prevalence of AIDS6 added to the caseload, so that a total of over 52,000 unexpected US cases of active TB occurred by 1992, a pattern that has continued.
Emergence of Drug-Resistant TB Strains
To compound the problem and increase its threat to HCWs, many of the new TB isolates were found to be resistant to isoniazid (INH) and/or other drugs, which are usually effective in treating this infection. Most ominous in this regard are the TB strains that are resistant to multiple combinations of such drugs, hence the term "multi-drug resistant TB" (MDRTB). Such MDRTB has infected at least 19 HCWs,7 eight of whom have died.
Action Steps to Reduce the Spread of TB
Recognition of the resurgence of TB, particularly the threat of MDRTB, has led the CDC to issue guidance on an updated basis aimed at limiting TB transmission, especially in health care facilities.2 OSHA has also published a Proposed Standard and Notice of Public Hearing in regard to occupational exposure to TB.8 Both the CDC guidelines and the Proposed Standard call for a TB infection-control program in each such facility, with the program to include a written control plan. The written plan is based on careful risk assessment for the institution as a whole, as well as analyses for specific components such as those in which high-risk activities occur.
Risk analysis will usually result in implementation of many of the following action steps9:
- Periodic training of HCWs to enhance awareness and maintain an appropriate index of suspicion for new TB cases.
- Appropriate management of patients likely to have undiagnosed TB, in emergency, ambulatory, and inpatient settings.
- Engineering controls, including the use of negative-pressure rooms, adequate air exchanges in rooms of patients with suspected TB, careful handling of contaminated air,10 stand-alone high-efficiency particulate air (HEPA) filter units,8 and adjunctive use of ultraviolet germicidal irradiation.
- Masking of patients with suspected TB prior to the initiation of effective therapy when patients are in uncontrolled areas of health care facilities. In situations in which a known or suspected active pulmonary TB patient refuses to wear a mask, questions as to available options should be directed to the institution's legal counsel or to the state public health department's legal counsel.
- Mandatory respiratory protection of HCWs in contact with TB patients, particularly when engaged in high-risk procedures such as bronchoscopy, intubation, sputum induction, surgery, and autopsy. Periodic training must include respirator fit testing and the proper care and use of respirators.
The effectiveness of a TB infection-control program is measurable by ongoing monitoring of tuberculin conversions among HCWs, scrutiny of clusters of such conversions, investigation of possible person-to-person transmission, and similar analyses. Local public health authorities may be able to provide assistance in investigating a cluster of PPD conversions in the workplace.
In health care settings, when tuberculin testing is done on a periodic basis, some individuals will exhibit a "booster" phenomenon; ie, an anamnestic response will increase the induration elicited by 5 Units of PPD. Employers should perform two-step TB testing of all newly hired HCWs who have not had tuberculin tests within the previous 12 months. This will avoid pseudoconversions, in which a booster effect can mimic an actual conversion from TB exposure later in their employment. The frequency of periodic PPD testing should be consistent with the results of risk assessments done in accord with CDC guidelines.9
The use of the Bacille Calmette-Guérin (BCG) vaccine in childhood should not be used as an explanation for a positive reaction to the second PPD in two-step testing but may explain 8- to 10-mm reactions in persons upon their initial tests. Similar reactions, sometimes larger in size, can occur because inhalation of atypical mycobacteria such as Mycobacterium avium-intracellulare or M. kansasii can cause such responses, but these effects will not usually confound serial PPD readings in adults.
An accurate monitoring of actual tuberculin conversions gives important information on the effectiveness of the overall TB control program. One must also be aware, however, that community exposures, rather than job-related ones, could be responsible for some of these tuberculin conversions.11 For an HCW, a conversion of a PPD should be considered work-related unless there was a known exposure to an identified pulmonary TB case outside the work environment. For HCWs in facilities where TB patients receive care, PPD reactions of 10-mm induration or more are considered positive.
When a true conversion does occur, the HCW should have chest radiographs as soon as possible to exclude active disease. In the great majority of cases, radiographs do not show active disease and six months of INH therapy is recommended (300 mg/day with 25 to 50 mg/day of pyridoxal phosphate) for HCWs 35 years of age or younger. Persons older than 35 may be at higher risk of isoniazid toxicity, and it should be prescribed with added caution, especially in the presence of liver disease or chronic use of ethanol, acetaminophen, or other hepatotoxic medications. Pyridoxine should also be used to prevent INH neurotoxicity.
For HCWs with a previously positive PPD, yearly surveillance should continue, with questions directed at symptoms compatible with pulmonary TB (persistent cough, hemoptysis, night sweats, weight loss, and/or persistent fatigue). If there is clinical suspicion of tuberculosis, the HCW should be further evaluated by a physician.
The HCW with active pulmonary disease requires immediate therapy with INH, plus two or three other antituberculosis medications, pending the results of sputum culture and sensitivity determination. HCWs who are found to have active disease may return to work, including patient care, after three consecutive daily sputum smears are negative for acid-fast organisms,3 provided they are responding clinically and radiographically to treatment.
Occupational physicians should take a leadership role in promoting an active TB-control program, not only in health care institutions12 but also in other settings where the workforce includes persons at special risk of acquiring and spreading this infection. Such persons include those listed in the ACOEM position statement described above and may include travel assistants and clerical and reception staff who may have the initial contact with persons with active TB, who have not yet been so identified.
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