A simple blood test called the Khatri blood test is developed by researchers at the Stanford University School of Medicine to diagnose active tuberculosis. The test, which works in adults and children, determines a gene expression “signature” that separates patients with active tuberculosis from those with either latent tuberculosis or other diseases.

The researchers say that the test is 86 percent sensitive in children and is accurate 99 percent of the time. This can be done in underdeveloped areas where basic clinical facilities are inaccessible.

The researchers say this is an upgrade from conventional TB diagnostic tests. Unlike the Khatri test, current tests such as the skin prick and interferon assays cannot distinguish patients with active TB from those who have been vaccinated or no longer sick from the disease and can even fail to detect TB in HIV patients. Another test is the sputum test, but this can be unreliable considering not all patients can produce sputum on the spot and those who are getting better cannot produce sputum, making it useless to determine the efficacy of TB treatments.

The study, published online in Lancet Respiratory Medicine on Feb. 19, states that the TB infection starts a chain reaction that alters the expression of human genes. Senior author Purvesh Khatri says the test determined changes in three genes that are consistent with an active TB infection. Additionally, the Khatri test can also show how a patient reacts to different treatments.

The World Health Organisation states that tuberculosis is an infectious bacterial disease caused by Mycobacterium tuberculosis. It is transmitted from person to person via droplets from the throat and lungs of people with TB.  Active TB symptoms include coughing, sometimes with sputum or blood, weakness, weight loss, fever, chest pains and night sweats. Patients undergo a six-month course of antibiotic treatments.

Wikimedia/ Centers for Disease Control and Prevention

Wikimedia/ Centers for Disease Control and Prevention

It affected 9.6 million people in 2014 and killed 1.5 million people in the same year. TB remains to be the leading killer of patients with HIV in 2015.