Simple blood test could aid in global TB fight

A blood test for tuberculosis that could make it easier to detect people with the infection and help save lives has shown promise in a new study.

Researchers led by Dr Sheng-Wei Pan of Taipei Veterans General Hospital in Taiwan reported the results of their study at the annual meeting of the Association for Diagnostics & Laboratory Medicine (ADLM) in Anaheim, California, saying the blood test could permit earlier diagnosis and allow treatment to start more quickly.

TB is caused by the bacterium Mycobacterium tuberculosis, which affects a quarter of the global population and in 5% to 10% of cases leads to active disease.

According to the World Health Organization (WHO), TB killed 1.23 million people in 2024, even though it is almost always curable with antibiotic therapy when M. tuberculosis is detected in the initial stages of disease progression.

The disease is typically diagnosed by assessing sputum samples, mucus secretions coughed up from the lungs and airways, but that can be problematic, according to Pan.

"Not all patients can produce sputum when they first seek medical care, especially those with early disease or those with low bacterial burden," he said, creating a desperate need for non-sputum-based diagnostic tools.

Pan's team studied an established biomarker in the blood produced by the bacteria, called ESAT-6, which until now has not proved effective at differentiating between active pulmonary TB, latent TB infection, TB exposure, or other lung diseases.

Using a new, highly sensitive biosensor, the scientists looked at ESAT-6 levels in blood samples from 217 subjects, some of whom had active pulmonary TB and a control group consisting of uninfected people, those with latent TB infections, infections caused by other mycobacterial species, and lung cancer.

They found that the test was not only highly effective at distinguishing between TB- and non-TB patients, but could also differentiate between uninfected people with TB contacts and those with latent TB.

Moreover, there are blood tests based on biomarkers that measure the body's immune response to infection, such as the Qiagen QuantiFERON test, but these cannot distinguish between dormant and active TB, require strict laboratory processing times, and can give false-negative results in immunocompromised individuals.

ESAT-6 has the advantage of being derived directly from the causative organism, according to Pan.

"We believe this is one reason why it performs so well in identifying active TB," he said. "We are currently planning a prospective study to further evaluate if this can be used in a real-world clinical setting."

Photo by National Institute of Allergy and Infectious Diseases on Unsplash