The test identifies antibodies associated with active disease, potentially offering a faster alternative to sputum samples and existing screening methods.
Researchers in the UC Davis Department of Pathology and Laboratory Medicine developed a new tuberculosis (TB) blood test designed to identify the active, infectious form of the disease. The discovery aims to enable faster diagnosis and treatment while helping prevent the spread of TB by quickly identifying contagious individuals.
Current TB screening tests do not differentiate between active TB disease and a latent, or inactive, infection. While TB is caused by the bacterium Mycobacterium tuberculosis, only those with active infections can spread the disease through coughing, sneezing, or speaking.
“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,” says Imran H Khan, a professor in the UC Davis Department of Pathology and Laboratory Medicine, in a release. “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.”
Addressing Diagnostic Limitations
Existing diagnostic tools often require additional follow-up testing after a positive result. Sputum tests, for example, can miss TB located outside of the lungs and are often difficult to obtain from children.
The new blood test measures the immune system’s response to TB proteins, similar to the interferon-gamma release assay (IGRA). However, unlike the IGRA, this test specifically detects antibodies associated with active tuberculosis. This allows clinicians to identify patients who are currently sick and contagious rather than those who have simply been exposed to the bacteria in the past.
“TB is often a disease of poverty, especially in developing countries,” says Khan in a release. “And like most other poverty-related problems, it is a major cause of human suffering worldwide.”
Clinical Trial Performance
The effectiveness of the test was evaluated in a clinical trial in India from 2019 to 2023, involving more than 600 participants. Results indicated that the test performed well in identifying adult pulmonary TB, which accounts for approximately 60% to 70% of infections.
“The test performed surprisingly well,” says Khan in a release. “In addition to the expected good performance in adult pulmonary TB…it was also able to identify harder-to-detect TB cases in children as well as TB that was in other organs in the body, not in the lungs.”
Data analysis and a clinical trial report have been submitted to the Indian Council of Medical Research (ICMR). If approved by the ICMR, the test could be expanded to neighboring countries. According to Khan, India, Pakistan, and Bangladesh alone account for approximately 30% to 40% of the global TB population.
To commercialize the technology, Khan co-founded AppGenex Diagnostics, a startup based in Mountain View, California.
“If we can stop the spread of TB by more easily identifying active infections, we can make a significant difference in decreasing global numbers of this devastating disease,” says Khan, a professor in the UC Davis Department of Pathology and Laboratory Medicine, in a release.
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