The use of nucleic acid amplification testing for tuberculosis increased in the United States between 2011 and 2017, although nearly half of U.S. TB cases did not include one of the tests, according to a study.
“In the United States, too many people still suffer from TB disease. Rapid diagnosis of TB is critical for getting patients on treatment and preventing transmission,”Angela Starks, PhD, laboratory branch chief in the CDC’s Division of Tuberculosis Elimination, told Healio.
“Nucleic acid amplification (NAA) testing is an important diagnostic tool that can reliably detect Mycobacterium tuberculosis DNA in specimens in just hours after receipt in the laboratory, compared to weeks for detection of M. tuberculosis organisms in culture,” Starks said. “In 2009, CDC recommended NAA tests for all patients with suspected pulmonary TB disease. We hoped to better understand the use of NAA testing and potentially identify opportunities for broader use of this valuable diagnostic.”
Starks and colleagues studied all verified cases reported to the National Tuberculosis Surveillance System in the from 2011 to 2017.
They found that, among all 67,082 verified TB cases with NAA testing information during that time, 45.9% were reported as not having an NAA test performed. However, they also found that the proportion of cases without NAA testing declined annually, from 60.5% in 2011 to 33.6% in 2017.
Among all verified cases, 41.6% had positive NAA test results, 12.2% had negative results and 0.2% had indeterminate NAA test results. Additionally, among 33,937 cases with an acid-fast-bacilli-smear-positive result, 70.9% had an NAA test performed, whereas 38% of the 30,244 with an acid-fast-bacilli-smear-negative result had an NAA test performed. The researchers noted that although sputum was the most common specimen type tested, 79.8% of nonsputum specimen types had a positive NAA test result.
“Challenges still exist in NAA’s broader use, especially among patients with nonsputum specimens, patients with extrapulmonary TB, patients with acid-fast-bacilli-smear-negative TB, and pediatric patients,” Starks said. “Health care providers with questions about NAA testing should consult with their state or local TB program or public health laboratory.”