The standards are endorsed by the Infectious Diseases Society of America. The statement describes diagnostic strategies for high- and low-risk patients and outlines a classification scheme for tuberculosis. Included are sections on the epidemiology of tuberculosis, transmission of Mycobacterium tuberculosis, pathogenesis, clinical manifestations, diagnostic microbiology including methods of collecting, handling and culturing specimens and drug susceptibility testing and tuberculin skin testing. The following discussion summarizes the classification scheme for tuberculosis and the interpretation of tuberculin skin test reactions.
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The standards are endorsed by the Infectious Diseases Society of America. The statement describes diagnostic strategies for high- and low-risk patients and outlines a classification scheme for tuberculosis. Included are sections on the epidemiology of tuberculosis, transmission of Mycobacterium tuberculosis, pathogenesis, clinical manifestations, diagnostic microbiology including methods of collecting, handling and culturing specimens and drug susceptibility testing and tuberculin skin testing.
The following discussion summarizes the classification scheme for tuberculosis and the interpretation of tuberculin skin test reactions. The classification scheme is as follows: 0. No tuberculosis exposure, not infected.
Tuberculosis exposure, no evidence of infection. The tuberculin skin test is negative in such patients. The guidelines specify that the action taken in these patients depends mainly on the degree of exposure toM. If a significant exposure has occurred within three months, a repeat skin test should be performed 10 weeks after the last exposure. In addition, initiation of treatment of latent tuberculosis should be considered, especially in children younger than 15 years and in patients with HIV infection.
Latent tuberculosis infection, no disease. This class is characterized by a positive reaction on tuberculin skin testing, but no clinical, bacteriologic or radiographic evidence of active tuberculosis.
Treatment of latent tuberculosis may be indicated in some patients. Tuberculosis, clinically active. This category includes all patients with clinically active tuberculosis whose diagnostic procedures are complete. The patient remains in class 3 until treatment of the current episode is completed.
Bacteriologic status, with specification of the test technique i. The results of drug susceptibility testing are also included. The findings on chest radiographs are classified as normal, abnormal, cavitary or noncavitary, and stable or worsening or improving.
Tuberculin skin test reactions are classified as positive or negative, with the size of the induration noted. Tuberculosis, not clinically active. This class includes patients with a positive tuberculin skin test reaction and a history of tuberculosis or abnormal stable radiographic findings.
The guidelines state that patients in this class may never have received chemotherapy, may be receiving treatment for latent infection or may have completed a previous course of chemotherapy. Tuberculosis suspect diagnosis pending. Tuberculin Skin Testing The accompanying table outlines the guidelines for determining a positive tuberculin skin test reaction. The guidelines define skin test conversion in persons with previously negative results as an increase in the reaction size of 10 mm or more within a period of two years.
Factors such as the common occurrence of poor nutrition and general health, overwhelming acute illness and immunosuppression appear to account for such a high false-negative rate. In view of an M. Thus, screening in low-risk groups is not recommended, because a false-positive result is more likely than a true-positive result. Reprinted with permission from American Thoracic Society. Diagnostic standards and classification of tuberculosis in adults and children.
Groups with a high prevalence of tuberculosis include persons born in countries with a high rate of tuberculosis, persons with poor access to health care, persons who live or spend time in facilities such as nursing homes, prisons, homeless shelters and drug treatment centers, and persons who inject illegal drugs.
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ATS Adopts Diagnostic Standards for Tuberculosis