A blood test for tuberculosis that could make it easier to detect people with the infection and help save lives has shown promise in a new study. TB is caused by the bacterium Mycobacterium tuberculosis, which affects a quarter of the global population and in 5% to 10% of cases leads to active disease. Pan's team studied an established biomarker in the blood produced by the bacteria, called ESAT-6, which until now has not proved effective at differentiating between active pulmonary TB, latent TB infection, TB exposure, or other lung diseases. They found that the test was not only highly effective at distinguishing between TB- and non-TB patients, but could also differentiate between uninfected people with TB contacts and those with latent TB. "We believe this is one reason why it performs so well in identifying active TB," he said.