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![Osh TB paediatric hospital](/sites/default/files/styles/image_mobile/public/images/MSF_TB72.jpg?itok=1r9gcuOY)
The most widely-used test for diagnosing active TB in low- and middle-income countries relies on examining a patient’s phlegm under a microscope. This method developed nearly 140 years ago, detects less than half of all TB cases and largely fails to detect the disease in children and people co-infected with HIV – who usually can’t produce the sputum needed – and those with drug-resistant forms of TB. A diagnostic test, Xpert MTB/RIF, was introduced, and we use it in many of our projects, but it can't be used in many resource-limited settings.