Patients at risk for latent or active tuberculosis (TB) infection should be assessed with newer tests, including interferon-gamma release assays (IGRAs) and molecular diagnostics, according to new guidelines on TB diagnosis published by IDSA with the American Thoracic Society (ATS), and Centers for Disease Control and Prevention (CDC) in Clinical Infectious Diseases. Advances in testing prompted the first new guidelines on TB diagnosis in 17 years.
TB spreads through the air and can be challenging to diagnose and treat. Up to 13 million Americans have latent TB. Only 5 to 10 percent ultimately go on to develop the disease itself, about half of those within two years of being infected. Treatment varies depending on whether the TB is latent or becomes active.
Because TB disease is less common in the United States, healthcare providers may overlook it as a possible diagnosis. The guidelines recommend healthcare providers consider testing for latent TB in patients who:
- Live with a person who has TB disease,
- Immigrated to the United States from a country where TB disease is common,
- Are in high-risk settings, such as prison.
If the patient does not have active signs of TB disease, the guidelines recommend testing be performed with one of two Food and Drug Administration-approved IGRAs, rather than using a tuberculin skin test (TST). If an IGRA is not available, a TST is acceptable. IGRAs test the blood and are more effective at detecting TB disease infection than a TST. IGRAs also are more practical because they can be done in one patient visit. The TST requires two visits and patients often don't return within the allotted two or three days to have results assessed.
If a person has a positive TST or IGRA, has no symptoms and the chest X-ray is normal, latent TB treatment to prevent progression to TB disease should be considered. If the X-ray suggests active disease, the doctor should order a combination of tests of sputum including smears, cultures and a nucleic acid amplification test. Molecular diagnostic testing results are more specific for TB disease than smears and available more quickly than cultures.
If a patient has active signs of TB disease, doctors should order smear, cultures and molecular diagnostic testing, particularly in patients at higher risk, such as those who have HIV or live with a patient with TB disease, the guidelines recommend. Symptoms of TB disease include ongoing fevers, night sweats, weight loss and coughing. If tests confirm TB disease, patients should be treated appropriately in conjunction with infectious disease and/or pulmonary physicians, as well as with the public health department. Much more intensive than treatment for latent TB, the regimen for TB disease includes a combination of four medications taken for six months. Treatment of antibiotic-resistant TB disease is even more complex.
Drug-resistant TB disease is becoming a significant problem, with about 500,000 cases of multi-drug resistant TB disease from 127 countries and extensively drug resistant TB disease reported in 105 countries.
Because TB is a complex disease, treatment should be provided by physicians with TB experience, such as infectious disease specialists or pulmonologists.
The guidelines have been endorsed by the European Respiratory Society.
In addition to lead author, David M. Lewinsohn, MD, PhD, the guidelines panel includes: David L. Cohn, MD, FIDSA; Charles L. Daley, MD; Ed Desmond, PhD; Joseph Keane, MD; Michael K. Leonard, MD, FIDSA; Deborah A. Lewinsohn, MD; Philip A. LoBue, MD; Ann M. Loeffler, MD; Gerald H. Mazurek, MD; Richard J. O'Brien, MD; Madhukar Pai, MD, PhD; Luca Richeldi, MD, PhD; Max Salfinger, MD, FIDSA; Thomas M. Shinnick, PhD; Timothy R. Sterling, MD, FIDSA; David M. Warshauer PhD; and Gail L. Woods, MD.
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