Shafaqna Health: Researchers in the UC Davis Department of Pathology and Laboratory Medicine have created a new tuberculosis blood test that can detect the active, infectious form of the disease. The discovery enables faster diagnosis and treatment. It also helps prevent the spread of tuberculosis (TB) by quickly identifying those who are contagious.
Current TB screening tests do not differentiate between active TB disease and a latent (inactive) infection. Positive TB tests must be followed up with additional tests.
However, these additional tests can also have limitations. For example, sputum tests can miss TB outside the lungs, and children usually can’t easily produce the sputum samples needed for accurate testing.
TB is caused by the bacterium Mycobacterium tuberculosis. It spreads when a person with an active infection coughs, sneezes, or speaks—putting close contacts like family, friends, coworkers and classmates at the greatest risk.
TB most often attacks the lungs but can strike almost any part of the body. Although it is generally curable with a long course of antibiotics, completing treatment can be difficult.
Despite being treatable, TB remains one of the world’s deadliest infectious diseases.
In 2024, an estimated 1.23 million people around the globe died from the disease, and about 10.7 million fell ill. In the U.S., more than 10,000 cases were diagnosed—2,000 of them in California.
The largest number of new TB cases occurred in South-East Asia, with India accounting for 25% of the global total.
“TB is often a disease of poverty, especially in developing countries,” explained Imran H. Khan, a professor in the UC Davis Department of Pathology and Laboratory Medicine. “And like most other poverty-related problems, it is a major cause of human suffering worldwide,” he said. His desire to help alleviate global poverty was a key motivation for developing the new test.
Mantoux Tuberculin Skin Test. In this test, a small amount of sterile tuberculin protein is injected into the skin. If the TB skin test shows a bump within two to three days, it indicates exposure to TB.
Interferon-gamma release assay (IGRA). This blood test assesses how the immune system responds when a small amount of the patient’s blood is mixed with TB proteins. A positive test result indicates the blood has reacted to TB proteins, signaling infection.
The challenge is that neither test type distinguishes between active TB (the patient has the disease) or latent infection (the patient had exposure to TB but is not currently sick). Only active TB disease is contagious.
Khan explains, “About 35% to 40% of the general population in TB-endemic countries is latently infected—meaning they have been exposed—but they may never develop TB. A test that gives a positive result with latent infection is not useful in finding active TB cases in which someone might have the disease and inadvertently spread it to others.”
