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A new test called Xpert MTB/RIF
detected approximately two thirds of TB cases found by the current culture test
in significantly less time. Generally, a preliminary diagnosis requires the
examination of a sample of lung secretions under a microscope to determine if
it contains TB bacteria. In addition, a sample is sent to a laboratory to be
cultured and identified; a lab culture test can take as long as six weeks to
show a positive result. Children have less infectious bacteria than adults,
which increases the level of difficulty in detecting the bacteria under a
microscope or growing a culture.
In a study sponsored by the US
National Institutes of Health (NIH), researchers in South Africa collected
approximately 1,500 samples from approximately 400 children who presented at a
primary care clinic with TB symptoms. Trained clinical staff with special
equipment collected samples of secretions from the children’s lungs, nasal
passages, or both. The researchers compared results from the Xpert MTB/RIF test
with the microscope detection test and laboratory culture test. Of the 30 TB
cases detected by culture, the Xpert test diagnosed 19 (63 percent) positive
cases while microscopic examination only detected 4 cases (13 percent). Adding
a second test with additional samples improved detection rate for both tests.
Xpert MTB/RIF results were available
in an average of 24 hours compared with more than two weeks for the culture
test. Results indicated that ease and timeliness of diagnosis with the Xpert
MTB/RIF were important for clinics in resource-limited countries where
equipment for traditional tests might not be available. The test also
identified strains of TB resistant to rifampicin, which helped clinicians
determine the right treatment. This is particularly important for countries
where drug-resistant strains are common. The Xpert MTB/RIF test was 99-percent
accurate in identifying children who did not have TB.
NIH’s National Institute of Allergy
and Infectious Diseases funded the development of the Xpert MTB/RIF test and
the National Institute of Child Health and Human Development funded the Xpert
MTB/RIF testing examined by this study.
The full report, “Rapid Diagnosis of
Pulmonary Tuberculosis in African Children in a Primary Care Setting by Use of
Xpert MTB/RIF on Respiratory Specimens: A Prospective Study,” was published
online in the journal Lancet Global Health (2013;
doi:10.1016/S2214-109X(13)70036-6).
The Friends of AIDS Foundation is
dedicated to enhancing the quality of life for HIV positive individuals and
empowering people to make healthy choices to prevent the spread of the HIV
virus.
To learn more about The Friends of
AIDS Foundation, please visit: http://www.friendsofaids.org.
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