The new Khatri blood test could radically alter the way medical professionals test for tuberculosis in the nations of the developing world. This simple blood test could also serve to identify which patients have active infections, and serve in treatment of the disease.

Tuberculosis (TB) is a disease that can result from an infection by the bacteria Mycobacterium tuberculosis. Most of these cases strike the lungs, but the microorganisms can also infect other organs, including the brain, spine or kidney. Infections are spread when infected people sneeze, cough, speak or sing near those without the disease. The bacteria cannot be spread by sharing food, drink, toothbrushes, or by kissing.

The disease can be fatal, and was once the most common cause of death among Americans. Hundreds of millions of people worldwide are infected with the potentially-fatal bacteria, which takes the lives of 1.5 million people annually.

"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 of the Stanford University School of Medicine.

Previous tests for TB involved examining the sputum, heavy respiratory secretions of potentially-infected patients. One of the problems with this testing method is that it becomes increasingly difficult for doctors to obtain samples as patients recover and mucus is reduced.

The new diagnostic method is 86 percent effective in children, and does not produce false positives among those who have been immunized against the disease, or those with an inactive infection. Negative results in patients are 99 percent accurate, researchers report. The Khatri test identifies a gene expression signature present only in those with active TB infections.

Older diagnostic methods could also miss TB infections in patients with HIV infections. The new test is able to successfully detect the disease in HIV-positive subjects. As doctors work with patients fighting TB, the Khatri test can be used to monitor the health of patients and to track the effectiveness of various treatment methods.

The new test is designed to be quick and inexpensive. This means that health care centers in the developing world should have the facilities to easily diagnose and treat local populations.

Development of the new blood test for TB was detailed in the journal Lancet Respiratory Medicine.

Photo: Day Donaldson | Flickr

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