Tuberculosis in the Workplace (2001) / Chapter Skim
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2 Basics of Tuberculosis
2 Basics of Tuberculosis
Pages 24-42
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From page 24... ...
An understanding of both latent tuberculosis infection and active tuberculosis is needed to develop effective policies and programs to prevent and control transmission of tuberculosis in communities generally and in workplaces specifically. Detection and treatment of active, transmissible disease is the highest priority for both clinicians and public health officials.
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From page 25... ...
25 Latent Tuberculosis Infection Few tuberculosis bacteria in the body Tuberculin skin test reaction usually but not always positive Chest radiograph normal Sputum smears and cultures negative No symptoms Not infectious Many tuberculosis bacteria in the body Tuberculin skin test reaction usually but not always positive Chest radiograph usually abnormal Sputum smears and cultures usually ., . positive Symptoms (e.g., cough)
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From page 26... ...
Tuberculosis is considered moderately infectious, with infection developing in perhaps 30 to 50 percent of those who have extended, close, indoor contact with people with active disease. Measles, by contrast, is considered highly infectious, with infection developing in an estimated 80 percent of susceptible people who come in contact with an infected individual (Haas and Des Prez, 1995~.
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From page 27... ...
As discussed further below, treatment of latent tuberculosis infection substantially reduces the risk of progression to active disease. 7Age-specific disease patterns differ in high- versus low-prevalence countries ~Comstock, 2000; Daniel, 2000~.
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From page 28... ...
High-risk groups include people with HIV infection and certain other medical conditions, recent immigrants from countries where tuberculosis is common, and those with recent exposure to someone with infectious tuberculosis. Treatment for latent tuberculosis infection should be available to those who have positive tuberculin skin test results.
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From page 29... ...
is injected into the skin of the forearm by a health care worker trained in the procedure. The only skin testing procedure recommended by CDC is the tuberculin skin test with PPD (a purified protein derivative of tuberculin)
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From page 30... ...
who have positive test results.9 The lower the sensitivity of a test, the more likely a test will miss people who actually have the disease or condition but show false-negative test results. The sensitivity of the tuberculin skin test has been estimated at 95 percent except for those with active tuberculosis or very recent infection (ATS/ CDC, 1999a, Appendix B)
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From page 31... ...
A test's positive predictive value is affected by the prevalence of the disease or condition in the community of those being tested.~° Table 2-3 illustrates how prevalence affects calculations of positive predictive value for the tuberculin skin test. Another way of understanding the effect of disease or condition prevalence relies on Bayesian analysis, as shown in Table 2-4.
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From page 32... ...
With good training and careful practice, the tuberculin skin test is not difficult to administer correctly and to interpret accurately and consistently. A lack of resources and inadequate training and oversight can, however, jeopardize the proper storage of the test material, the quality of testing procedures, and the appropriate recording and use of test results (Chaparas et al., 1985; Ozuah, 1999; see also Perez-Stable and Slutkin [1985~.
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From page 33... ...
and other similar locales around the world, common exposure to mycobacteria other than M tuberculosis can produce false-positive tuberculin skin test results.
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From page 34... ...
These additional limitations of the tuberculin skin test need to be recognized in implementing skin testing programs and developing policy recommendations and requirements for community and workplace programs for tuberculosis surveillance. As recommended in the recent Institute of Medicine report on the elimination of tuberculosis in the United States (IOM, 2000)
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From page 35... ...
Side Effects of Treatment The major concern about treatment of latent tuberculosis infection has been the potential for liver damage. A recent analysis of 7 years of experience at a Seattle public tuberculosis clinic suggests that the risk of liver damage form the most widely used drug (isoniazid)
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From page 36... ...
The highest rates of completion of treatment among health care workers were reported in a study of a hospital in a city with relatively high rates of active tuberculosis (Blumberg et al., 1996~. Of 125 workers with a recent positive tuberculin skin test result, all got a chest radiograph and almost all (98 percent)
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From page 37... ...
and the smears as AFB positive or negative.) The clinical case definition of tuberculosis requires all of the following: a positive tuberculin skin test result, other signs and symptoms compatible with active tuberculosis (e.g., abnormal and unstable radiologic findings and persistent cough)
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From page 38... ...
Improving Diagnostic Timeliness and Accuracy Failures to promptly identify, isolate, and treat those with diagnosed or suspected infectious tuberculosis are major weak points in programs to prevent occupational exposure to the disease. Unfortunately, communityand workplace-based efforts to improve timely and accurate diagnosis of 13A tuberculin skin test is optional.
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From page 39... ...
Clinicians likewise may not initially link radiologic signs of active tuberculosis to the disease. Moreover, some individuals with active tuberculosis, especially those with HIV infection, may show radiologic signs that are not typical of the disease, and a few may experience no symptoms.
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From page 40... ...
As noted earlier, treatment of active tuberculosis cuts death rates from 50 percent or more to near zero for immunocompetent people who have drug-sensitive disease and who receive timely, appropriate care. Unfortunately, multidrug-resistant strains of tuberculosis are much more difficult to treat, especially for patients with poorly functioning immune systems.
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From page 41... ...
6~. For individuals not living in prisons, nursing homes, or similar settings, directly observed treatment may involve scheduled appointments that bring a patient to a physician's office, clinic, or other site so that a nurse or other trained individual can watch the person take the required medications.
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From page 42... ...
The next chapter reviews the statutory basis for the 1997 proposed OSHA rule on occupational tuberculosis. Chapter 4 compares the proposed rule with the 1994 CDC guidelines to prevent transmission of tuberculosis in health care facilities.
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