A simple blood test that can be used to accurately diagnose active tuberculosis (TB) could make it easier and cheaper to control a disease that kills 1.5 million people every year. Researchers at the Stanford University School of Medicine have identified a gene expression "signature" that distinguishes patients with active TB from those with either latent TB or other diseases. The technology fills a need identified by the World Health Organization (WHO), which, in 2014, challenged researchers to develop better diagnostic tests for active TB. A paper describing the new work was published online in Lancet Respiratory Medicine on February 19, 2016. The article is titled “Genome-Wide Expression for Diagnosis of Pulmonary Tuberculosis: A Multicohort Analysis.” An editorial, entitled “Defining a Diagnostic Gene Signature for Tuberculosis,” accompanies the article. Globally, TB infects 9.6 million new patients each year and kills 1.5 million. Yet, the disease remains difficult to diagnose. "One-third of the world's population is currently infected with TB. Even if only 10 percent of them get active TB, that's still 3 percent of the world's population -- 240 million people," said Purvesh Khatri, Ph.D., Assistant Professor of Medicine and senior author of the paper. Traditional diagnostic methods, such as the skin prick test and interferon assays, can't separate patients with active TB from those who are no longer sick or who have merely been vaccinated against TB (and most countries vaccinate everyone against TB). These older diagnostics can also miss a case of TB in patients with HIV. A common way to test for TB is to look for the disease-causing bacterium in sputum samples coughed up by patients. But sometimes it's hard for people to produce sputum on demand, said research associate Tim Sweeney, M.D., Ph.D., first author of the paper.
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