Xpert MTB/RIF was developed with funding from the NIH’s National Institute of Allergy and Infectious Diseases. Testing of Xpert MTB/RIF in children was funded by NICHD.
Preliminary diagnosis of TB is often made by collecting a sample of lung secretions and examining the sample under a microscope to see if it contains the bacteria that cause TB. A sample is also sent to a laboratory so the bacteria can be cultured and identified. It may take as long as six weeks for the culture test to show a positive result. Because, children have lower levels of infectious bacteria than do adults, it is more difficult to detect the bacteria under a microscope and to grow it in a culture. For this reason, accurately diagnosing TB in children has been difficult.
The World Health Organization estimated that in 2011 there were 500,000 TB cases and 64,000 deaths among those younger than 15 years .
Dr. Zar and her colleagues collected almost 1500 samples from nearly 400 children who went to a primary care clinic with symptoms of TB. Collecting the samples—secretions from the lungs, the nasal passages or both—requires special equipment and trained clinical staff. The researchers compared the results from the Xpert MTB/RIF test, examination of samples under a microscope, and from growing the tuberculosis bacteria in laboratory cultures. Bacterial culture is the most accurate method for diagnosing TB.
Of the 30 TB cases detected by culture, 19 (63 percent) were positive by the Xpert MTB/RIF test on lung or nasal samples, while examining the samples under the microscope turned up only four cases (13 percent). Adding a second test (of a second lung or nasal passage sample) improved the detection rate for both culture and Xpert MTB/RIF.