New TB diagnostic tool could lower costs

KISUMU, 18 July 2014 (IRIN) – Early results from a clinical trial indicate that an enzyme based TB detection method could diagnose the disease in 30 minutes and further lower the cost of diagnosis by up to 40 percent, according to authors of a new study.

With the help of a chemical called CDG-3 which glows when it is broken down by an enzyme called BlaC – produced by mycobacterium tuberculosis, the bacterium that causes TB – the researchers were able to show the presence of the TB-causing bacteria.

“This discovery has the potential to serve as a frontline tool in developing countries, allowing health providers to deliver results in 10 minutes and begin treatment in the same patient within the same session. It could be the answer to the World Health Organization’s [WHO] mission to eradicate the disease across the globe,” Jeffrey Cirillo, the study’s lead researcher and professor at the Texas A&M Health Science Center College of Medicine, told IRIN.

“What one needs is to take a sputum sample, treat it with the reactive solution and put it inside the reader. And a camera mounted inside will look for reaction between the sample and solution that produces light. When there is no light it means no infection,” he said.

According to the researchers, “results show that the test can determine a patient‘s TB infection with up to 86 percent sensitivity and 73 percent specificity, thus demonstrating its potential as a low-cost point-of-care test for use in resource-limited areas.”

TB diagnosis tools in use currently have not been able to target a specific TB enzyme for diagnosis.

The test will require little technical expertise or resources, since the technology is user friendly.

The test, which is currently in the later stages of clinical trials in the USA, Peru, Thailand and Vietnam, is expected to be rolled out to the market in the next 18 months and will cost US$5 for each test.

“Even though the specificity of the test appears low and will need further work, the finding … suggests that a beta-lactamase detection approach may have promise for TB diagnosis,” Madhukar Pai, associate professor of McGill University and associate director of McGill International TB Centre, told IRIN by email.

Time-consuming smear microscopy

The smear microscopy which is currently widely used in resource-poor settings to diagnose TB has a significantly lower ability to detect TB, ranging between 50 to 60 percent sensitivity. It is also time-consuming and often requires expensive instruments.

In many developing countries lacking resources to screen and follow up with infected people, patients with active TB only have a 50 percent chance of survival, according to WHO.

Currently, an average of 10 to 15 people with untreated active TB succumb to the disease each year. WHO says it needed to bridge a US$2 billion annual gap in order to meet its overall requirement of up to US$8 billion a year to fight the disease in low and middle-income countries.

According to McGill University’s Pai, “there is growing need for a test that can be done at the community level by health workers.”

This, he noted to IRIN, will speedily identify those persons who need confirmatory testing for the disease.

“The beta-lactamase test, if proven to be accurate and effective, and might fit this niche,” he said.

Calls for caution

Even so, some have called for a cautious approach. “We certainly need new point-of-care diagnostics for TB but I think it is better to speak to the need for further testing of such diagnostics in the lab and in the field,” Ted Cohen, associate professor in medicine, division of global health equity at Brigham and Women’s Hospital in the department of epidemiology, Harvard School of Public Health, told IRIN by email.

He added: “There are many early stage tests and this one, so far, does not yet stand out as something worth flagging until we see more and more promising results.”

McGill’s Pai told IRIN it would be useful to test “the performance characteristics of this test in much larger validation trials, and ascertain the “independence of the test developers…

“If proven to be accurate and reliable, then it could undergo field studies in high TB burden settings. This could pave the way towards a WHO policy process.”


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