Washington D.C: Most commonly-used tuberculosis (TB) tests usually fail to detect the disease in the patients with HIV, but now a team of researchers has come up with a new blood test, claiming that it can signal a TB infection even if an individual also has HIV.
The simple blood test, which can accurately diagnose active tuberculosis, 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 tuberculosis from those with either latent tuberculosis or other diseases.
The technology fills a need identified by the World Health Organization, which in 2014 challenged researchers to develop better diagnostic tests for active TB.
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 senior author Purvesh Khatri.
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 have merely been vaccinated against TB. These older diagnostics can 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 first author Tim Sweeney.
The new test developed in the Khatri lab works on an ordinary blood sample and removes the need to collect sputum. It can signal a TB infection even if the individual also has HIV. And it won’t give a positive response if someone only has latent TB or has had a TB vaccine. It also doesn’t matter which strain of TB has infected a person or even if it has evolved resistance to antibiotic drugs. The test works in both adults and children.
The Khatri test is 86 percent sensitive in children and if the test comes up negative, it’s right 99 percent of the time. That is, of 100 patients who test negative with the Khatri test, 99 do not have active TB.