Large-scale study underscores value of routine Xpert testing on TB, MDR TB case finding

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genexpertA study of more than 100,000 patients with suspected tuberculosis at 18 sites across India showed that routine testing using Xpert molecular technology rather than the most commonly used — and oldest — diagnostic tool of examining a sputum smear under a microscope, increased detection of TB by 39 percent and led to five times the rate of detecting resistance to a TB treatment medicine.

In India, home to the largest tuberculosis epidemic in the world, national policy recommends examining sputum smears under a microscope first, followed by examination of additional samples, X-ray and clinical judgement in the event TB is not detected in a first sample under a microscope. The study, led by Kuldeep Singh Sachdeva of India’s Central TB Division, sought to determine if replacing smear microscopy with Xpert would lead to more patients being diagnosed early, and at the same time, detection that a patient’s tuberculosis is resistant to rifampicin, one of the first drugs normally to treat the disease. India’s policy currently recommends testing to determine drug sensitivity only for patients at high risk of resistance to drugs. The study found that among patients found to have drug-resistant tuberculosis, nearly a third had no prior history of TB treatment. The study is the first large-scale attempt in India to offer universal tuberculosis drug-sensitivity testing to all patients in whom TB is suspected in public health settings.

Of the 18 sites where the study took place four were in remote, sparsely populated areas, six were in urban areas and eight were in rural areas. Researchers gathered data at 14 of the sites for two to five months before beginning the intervention of replacing smear microscopy with Xpert diagnosis, and began the intervention immediately at four sites. Laboratory technicians at the sites received a one day training on using Xpert according to the manufacturers instructions.

The study which concludes that routine use of Xpert could lead to increased detection of tuberculosis and drug-resistant tuberculosis, is reported on PLOS ONE in Use of Xpert MTB/RIF in Decentralized Public Health Settings and Its Effect on Pulmonary TB and DR-TB Case Finding in India.

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