Study Shows New Test May Lower TB Rates

A new test for tuberculosis could efficiently reduce the prevalence of TB in southern Africa by over 28 percent, according to a study released last week by researchers at the Harvard School of Public Health.

The new automated DNA test, Xpert, has the potential to cost-effectively combat TB, which is thought to infect over one-third of the world’s population. According to lead author Nicolas Menzies, a Ph.D. candidate in health policy at HSPH, Xpert is more sensitive than traditional diagnostic tests, which only accurately identify about fifty percent of cases.

A greater number of countries have begun to adopt Xpert since the World Health Organization recommended its use in treating cases of TB suspected to be multi-drug resistant or HIV-associated, which are thought to be particularly dangerous.

“This test is one of the most significant developments in TB control options in many years,” Menzies said in an HSPH press release. “Our study is the first to look at the long-term consequences of this test when incorporated into routine health programs.”

Using mathematical models to project the potential consequences of implementing Xpert over 10- and 20-year periods in five southern African nations, the researchers found that implementation would avert 182,000 TB deaths and 132,000 TB cases in southern Africa over the next 10 years.

“Adopting this test does look like it would do what’s promised,” Menzies said. Menzies also added, however, that they did not see as significant of a reduction in incidence, the number of new cases each year, as they would have expected.

Looking at the cost of the test, Menzies said that it was not the “slam dunk” the researchers had expected, partially because of the increased treatment costs of surviving patients saved by Xpert.

Menzies also pointed out that conclusions would be very different in other regions, a further problem he’s interested in working on.

This article has been revised to reflect the following correction:

CORRECTION: Nov. 26

An earlier version of this article incorrectly stated that the new tuberculosis test Xpert would reduce costs to the health care system. In fact, Xpert is projected to cost the health system $401 million to $520 million over 10 years.