The world’s only diagnostic tool that can detect multi-drug resistant tuberculosis (MDR TB) in less than two hours time instead of the present method than can take upto two months, has passed the litmus test.

The Xpert MTB test that is presently being analysed by India and is expected to be rolled out across the country soon, has been found to accurately and quickly detect TB.

A review published on Friday, which assessed the diagnostic accuracy of the test was found to simultaneously detect TB and resistance to rifampicin, as an indicator of MDR.

Like sputum smear microscopy, which relies on detecting TB with a microscope in a laboratory, Xpert requires a sample of sputum.

However, while thousands of bacteria must be present in each millilitre of sample for TB to be detected under the microscope, Xpert can detect TB bacteria at much lower concentrations.

In addition, the conventional microscopy approach does not detect drug resistance. Instead, TB has to be grown in the lab.

This presents problems, especially for MDR TB, due both to the length of time required for the cultures to grow and the specialized laboratories and highly skilled staff needed.

The researchers, from the Cochrane Infectious Diseases Group (CIDG), McGill University and the Foundation for Innovative New Diagnostics (FIND), analysed data from 18 studies involving a total of 7816 people and found that when Xpert is used to screen 1,000 people, 150 of whom have TB, it picks up 132 of the 150 cases (88%) and falsely diagnoses 17 (2%) with TB.



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February 3, 2013