A rapid molecular test kit – the size of a microwave — has undergone a successful trial in a resource poor, primary-care setting by detecting both TB and multi-drug resistant TB in just 90 minutes. While the same sample took three days to confirm through a microscopy test — most prevalent now — and 106 days through a culture test.
The findings of the study, carried out simultaneously in India’s Christian Medical College, Vellore; South Africa, Peru, Azerbaijan, the Philippines and Uganda and published in the medical journal “The Lancet”, said the Xpert MTB/RIF test eventually reduced delays in diagnosis and treatment, and thus reduced morbidity and mortality.
The test was conducted on 6,648 patients of which 1,033 were found to be TB positive. Interestingly, 90% of these cases were detected by Xpert when 77% of these cases were found to be negative through microscopy.
The kit’s specificity rate – how many of those who are found positive are actually positive of TB — was 98.3% and its sensitivity – how many of the total cases did it detect — stood at 90.3%. In India, it tested 902 patients and found 101 to have TB with 7 being multi-drug resistant.
Two of the three key infectious diseases that afflicts humans — HIV and malaria — can be diagnosed in primary-care settings with simple rapid tests. No such technology has been available to accurately detect TB and its drug-resistant forms.
Dr Mark Perkins from FIND (Foundation for Innovative New Diagnostics), Switzerland, told TOI, “Most people once tested fast could be detected early. This will ensure reduced transmission to hapless people. But there is one problem. The instrument is too expensive for most countries that have a high burden of TB like India. The machine costs $17,000 and each test costs $17.
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