FROM CLINICAL INFECTIOUS DISEASES
A Clinical Practice Guideline for diagnosing pulmonary, extrapulmonary, and latent tuberculosis in adults and children has been released jointly by the American Thoracic Society, the Centers for Disease Control and Prevention, and the Infectious Diseases Society of America.
The American Academy of Pediatrics also provided input to the guideline, which includes 23 evidence-based recommendations. The document is intended to assist clinicians in high-resource countries with a low incidence of TB disease and latent TB infection, such as the United States, said David M. Lewinsohn, MD, PhD, and his associates on the joint task force that wrote the guideline.
There were 9,412 cases of TB disease reported in the United States in 2014, the most recent year for which data are available. This translates to a rate of 3.0 cases per 100,000 persons. Two-thirds of the cases in the United States developed in foreign-born persons. “The rate of disease was 13.4 times higher in foreign-born persons than in U.S.-born individuals (15.3 vs. 1.1 per 100,000, respectively),” wrote Dr. Lewinsohn of pulmonary and critical care medicine, Oregon Health & Science University, Portland, and his colleagues.
Even though the case rate is relatively low in the United States and has declined in recent years, “an estimated 11 million persons are infected with Mycobacterium tuberculosis. Thus … there remains a large reservoir of individuals who are infected. Without the application of improved diagnosis and effective treatment for latent [disease], new cases of TB will develop from within this group,” they noted ( Clin Infect Dis. 2016 Dec 8;64:e1-33. doi: 10.1093/cid/ciw694 ).
Among the guidelines’ strongest recommendations:
• Acid-fast bacilli smear microscopy should be performed in all patients suspected of having pulmonary TB, using at least three sputum samples. A sputum volume of at least 3 mL is needed, but 5-10 mL would be better.
• Both liquid and solid mycobacterial cultures should be performed on every specimen from patients suspected of having TB disease, rather than either type alone.
• A diagnostic nucleic acid amplification test should be performed on the initial specimen from patients suspected of having pulmonary TB.
• Rapid molecular drug susceptibility testing of respiratory specimens is advised for certain patients, with a focus on testing for rifampin susceptibility with or without isoniazid.
• Patients suspected of having extrapulmonary TB also should have mycobacterial cultures performed on all specimens.
• For all mycobacterial cultures that are positive for TB, a culture isolate should be submitted for genotyping to a regional genotyping laboratory.
• For patients aged 5 and older who are suspected of having latent TB infection, an interferon-gamma release assay (IGRA) is advised rather than a tuberculin skin test, especially if the patient is not likely to return to have the test result read. A tuberculin skin test is an acceptable alternative if IGRA is not available, is too expensive, or is too burdensome.
The guideline also addresses bronchoscopic sampling, cell counts and chemistries from fluid specimens collected from sites suspected of harboring extrapulmonary TB (such as pleural, cerebrospinal, ascetic, or joint fluids), and measurement of adenosine deaminase levels.
This work was supported by the American Thoracic Society, the Centers for Disease Control and Prevention, and the Infectious Diseases Society of America, with input from the American Academy of Pediatrics. Dr. Lewinsohn reported having no relevant financial disclosures; his associates reported ties to numerous industry sources.
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