The new technique detects heat produced by Mycobacterium tuberculosis

Flickr/Sanofi Pasteur

A potentially cheaper and faster method for diagnosing tuberculosis (TB) has been developed by researchers who hope to test it in Tanzania.

The lack of a cheap, quick and accurate test makes it hard to control the TB epidemic, which claims millions of lives every year in developing countries.

Culture-based methods are the gold standard for TB tests in the developing world, but these can take nearly 60 days to give a result.

"A cheap and fast, culture-based method could therefore decrease diagnostic time and patient treatment," Olivier Braissant a researcher at the University of Basel, Switzerland, and one of the study's authors, told SciDev.Net.

Molecular tests, such as GeneXpert, unlike culture-based methods, are fast, accurate and can detect drug-resistant strains. But the high costs and need for laboratories make access an issue for developing countries.

The new method, published in the Journal of Applied Microbiology earlier this month (18 August), uses a microcalorimeter to detect heat produced by Mycobacterium tuberculosis, the bacterium that causes TB, on a growth medium.

The study showed that detection takes 4–5 days but Braissant said that more sensitive microcalorimeters could detect tuberculosis in 24 hours.

"We made our own instrument with very simple and inexpensive parts for a very low cost of US$1,000 [some rapid detection methods cost more than US$39,000] so we really believe that our method has a strong potential for places with very limited resources," he said.

Braissant and his team are working with the Swiss Tropical and Public Health Institute to test the method at the Ifakara Health Institute in Tanzania.

He hopes the test will be ready for use within two years but acknowledges that it might take longer for the WHO to endorse it.

But Ruth McNerney, who studies pathogen biology and diagnostics at the London School of Hygiene and Tropical Medicine, United Kingdom, and is a member of the Stop TB Partnership's working group on new diagnostics, told SciDev.Net: "I don't think this test has any added value as a TB diagnostic test in developing countries where microbiology culture facilities for TB are rare.

"The study does not confirm the presence of bacteria, only the fact that something is growing, and you would then need to do a confirmatory test," she said.

Braissant explained that a confirmatory test is required, but said that microcalorimetry could determine which M. tuberculosis strains are drug-resistant, because these would continue growing after treatment.

Link to abstract in Journal of Applied Micobiology