New Blood Test for Active Tuberculosis

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.

WHO has called for a test that would give a positive result at least 66 percent of the time when a child has active TB. 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.

When pathogens infect the cells of the body, the infection sets off a chain reaction that changes the expression of hundreds of human genes. Khatri’s team identified three human genes whose expression changes in a consistent pattern, revealing the presence of an active tuberculosis
infection. The team validated the new three-gene test in a separate set of 1,400 human samples from 11 different data sets, confirming the diagnostic power of the test.

The new test not only accurately distinguishes patients who have active tuberculosis, it could also be used to monitor patients to see if they are getting better and how well they are responding to different
treatments.

The requirements of the test are simple enough that it can potentially be done under relatively basic field conditions in rural and undeveloped areas of the world. Any hospital should be able to perform the test. Villages without electricity could likely use ordinary blood samples and a solar-powered PCR machine, which multiplies strands of DNA, to accurately test people for active TB.

Read more:
Blood test could transform tuberculosis diagnosis, help monitor treatment effectiveness


Source: News Center |Stanford Medicine