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Updated IDSA, CDC guidelines recommend newer tests for TB
Physicians should use newer tests, such as interferon-gamma release assays or molecular diagnostics, for patients at risk for active or latent tuberculosis, according to new guidelines from the CDC, American Thoracic Society and Infectious Diseases Society of America.
As many as 13 million people in the United States may have latent TB, although only 9,557 active TB cases were reported in 2015, two-thirds of which were in foreign-born residents, according to a press release from IDSA. The 23 new recommendations, published in Clinical Infectious Diseases and endorsed by the European Respiratory Society, represent the first update on diagnosing TB in 17 years.
“These guidelines develop a structured approach to testing, recommending that doctors test for latent TB in patients who are at risk for infection and who would benefit from treatment, and for TB disease in patients who have signs and symptoms of the disease,” David M. Lewinsohn, MD, PhD, of Oregon Health & Science University, Portland, and an author of the guidelines, said in a press release. “Even though TB disease is not common in this country, it’s important that doctors remember it’s still around, and that they should test patients when appropriate.”
Lewinsohn and colleagues recommended that patients at risk for TB, including those who live with someone already infected with the disease, residents who immigrated from a country where TB is common or patients in high-risk settings such as prison, be tested for latent disease. An interferon-gamma release assay is preferable to the standard tuberculin skin test (TST) in patients aged 5 years or older who are likely infected with TB, are good candidates for latent TB testing, have a low or intermediate risk for disease progression or are unlikely to return for TST reading, the guideline authors wrote. However, the TST is still acceptable in situations where the interferon-gamma release assay is too costly or burdensome.
If a patient tests positive but has normal chest X-rays, the guidelines recommend physicians consider latent TB treatment to prevent the disease from progressing, while patients with signs of active TB should undergo sputum testing, including cultures, smears and nucleic acid amplification.
Researchers also pointed out that drug-resistant TB is becoming increasingly common. According to the press release, 500,000 cases of multi-drug resistant TB have been identified in 127 countries.
“The ability to rapidly and accurately identify Mycobacterium tuberculosis as well as drug resistance reflects substantial advances,” Lewinsohn and colleagues wrote. “While rapid tests for TB diagnosis still have a sensitivity of 70%-90%, they may fail to detect paucibacillary pulmonary TB. They also remain relatively expensive, making them difficult to implement in high-burden, low-resource settings. Ideally, what is needed is a simple, inexpensive, rapid (ie, hours) test that is highly accurate. Rapid tests for detection of drug resistance are approaching the desired level of accuracy, at least for rifampin. However, these tests also are relatively expensive and need to be expanded to allow for detection of resistance to other TB medications. Such expansion is currently limited by gaps in knowledge of the molecular basis of resistance to most first- and second-line drugs. In this regard, improved functional tests for resistance may be useful.” – by Andy Polhamus
Disclosure: Lewinsohn reports no relevant financial disclosures. Please see the full study for a complete list of all other authors’ relevant financial disclosures.
Perspective
Back to TopLynn Horvath
The big thing I would tell people in the field is to always keep tuberculosis in your differentials. TB is not that common in the U.S., and usually when I see a patient with TB, they have been through numerous doctors getting care for community-acquired pneumonia, and they keep relapsing before somebody finally thinks about TB. In the meantime, multiple people are getting exposed to TB, perpetuating the low-lying incidence we have in the U.S.
The process of developing a guideline involves a lot of compromise, and there are not a lot of randomized controlled data being generated in the field of TB, particularly in the U.S. because it is not that common a disease. A lot of the guidelines, particularly the American Thoracic Society criteria, are very strict and require randomized controlled data before they will generate a guideline. Expert opinion is what we have to rely on with TB, and that is why we are seeing such a delay in updating many of the guidelines.
The advice that I would give is that if you have a patient with risk factors for TB, make sure you test for it. If they have a history of being born in a foreign country, or have spent time in homeless shelters or jails, or have immune suppression, make sure you entertain the diagnosis of TB and try to get the best test — rapid diagnostics, as well as the gold standard: culture.
Disclosure: Horvath reports no relevant financial disclosures.
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Lewinsohn DM, et al. Clin Infect Dis. 2016;doi:10.1093/cid/ciw694.