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Management of Health Care Workers after Inadvertent Exposure to Tuberculosis: A Guide for the Use of Preventive Therapy

William W. Stead, MD, MACP
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From the Arkansas Department of Health, Little Rock, Arkansas. Requests for Reprints: William W. Stead, MD, Tuberculosis Program, Arkansas Department of Health, 4815 West Markham Street, Little Rock, AK 72205. Acknowledgments: The author thanks the public health nurses of the Arkansas Department of Health and the Directors of Nursing of 230 Arkansas nursing homes for their help in efforts at tuberculosis control. Their carefully kept database made it possible to assess the effect of heavy exposure on elderly tuberculin reactors. The author also thanks Dr. Noreen A. Hynes for helping to organize the presentation of data and statistical analyses; Dr. Eugene Stead for his assistance in presenting the material in a form better suited for practicing physicians; Jack T. Crawford, PhD, for resurrecting three of the original cultures 7 years after an outbreak was recorded and M. Donald Cave, PhD, for doing restriction fragment-length polymorphism fingerprinting on these cultures; Drs. J. P. Lofgren and John W. Senner for their help in the early analysis of data; Dr. Joseph H. Bates for his many suggestions; and Christopher Murphy for his patience with the many revisions of the tables and figure.

Copyright ©2004 by the American College of Physicians

Ann Intern Med. 1995;122(12):906-912. doi:10.7326/0003-4819-122-12-199506150-00003
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Objective: To quantify the protection of previously infected persons from developing tuberculosis after intense exposure.

Setting: 6 hospitals and 22 nursing homes in which heavy tuberculosis exposure had occurred.

Measurements: Results of tuberculin skin tests before and after exposure and the development of tuberculosis among known reactors, both converters and nonconverters.

Intervention: All converters were given preventive therapy with isoniazid as soon as they could be identified. Nonconverters and previously known reactors were not treated.

Results: In 6 hospital outbreaks, largely aborted by prompt preventive therapy, 98 of 336 nonreactors (29%) showed skin test conversion, and, before therapy could be started, 19 (19% [95% CI, 12% to 29%]) had developed tuberculosis. No tuberculosis developed among the 238 nonconverters (0% [CI, 0% to 1.5%]) or the 76 known reactors who were not treated (0% [CI, 0.5% to 2%]). Tuberculosis developed in 5 of 209 known reactors (2.4% [CI, 0.8% to 5.5%]) in 22 nursing homes with heavy exposure, little more than 10 of 921 known reactors (1.1% [CI, 0.5% to 2%]) in 76 homes where there was no exposure (P = 0.17).

Conclusions: Healthy persons who remain nonreactive to tuberculin after heavy exposure have escaped infection and require no chemotherapy. However, if exposure is discovered immediately, it is wise to start preventive therapy in particularly heavily exposed nonreactors and discontinue it if the skin test result is still negative at 3 months. Persons who react after exposure fall into three groups: 1) converters, in whom the risk for tuberculosis warrants preventive chemotherapy, regardless of age; 2) reactors with no preexposure test results, who should be treated as converters; and 3) previously known reactors, in whom the risk for tuberculosis generally is too slight to warrant therapy. However, those who are younger than age 35 years, have human immunodeficiency virus infection, are receiving cancer chemotherapy or long-term corticosteroid therapy, or are otherwise immunocompromised should be considered for preventive therapy, regardless of the exposure.


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Figure 1.
General guidelines for managing the situation after an inadvertent exposure to tuberculosis.

Previously known tuberculin skin test reactors and those who remain tuberculin skin test negative 8 weeks after exposure require no therapy unless otherwise indicated by, for example, age or other risk factors. Those with tuberculin skin test conversions of 15 mm or greater should be treated preventively, regardless of age, provided they are clinically healthy and the chest radiograph shows no evidence of tuberculosis. Those with less definite evidence of new infection require individual consideration. Skin test reactors with no skin test record before exposure should be treated as if they had been nonreactors before exposure. Asterisk indicates that for persons younger than age 35 years, preventive therapy should be considered regardless of exposure. Dagger indicates that if the patient has been very heavily exposed, isoniazid therapy should be started. This therapy can be discontinued if the skin test result is still negative.

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