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The Centers for Disease Control and Prevention (CDC) is now recommending nucleic acid amplification (NAA) testing as part of the diagnostic criteria for tuberculosis (TB).
NAA testing can quickly and accurately confirm samples that are positive by acid-fast bacilli (AFB) smear microscopy, particularly in settings where non-tuberculosis mycobacteria are common. It also can confirm TB infection at least a week sooner than culture.
Culture remains the gold standard, however, and is required for resistance testing.
Currently, NAA testing is not widely used in the
United States, in part because clinicians have been uncertain about its value and cost-effectiveness. But CDC noted that recent studies have found that where NAA tests are used, they frequently provide the deciding factor in starting therapy. And although NAA testing is expensive, CDC said it will result in net savings because faster TB diagnosis will reduce the chances for transmission. Screening out negative cases more quickly will save the costs of isolation and contact investigations.
CDC says speeding up diagnosis of TB in patients suspected of having pneumonia will reduce the inappropriate use of empiric fluoroquinolone monotherapy, which is likely contributing to the development of fluoroquinolone-resistant TB.
The revised recommendations and testing algorithm are published in the Jan. 16 Morbidity and Mortality Weekly Report. They were developed by CDC and the Association of Public Health Laboratories.
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