Researchers find that quantifying the ESAT-6 protein in blood can differentiate active infection from latent cases and other lung diseases.
A new study presented at the Association for Diagnostics & Laboratory Medicine (ADLM) 2026 meeting suggests that a blood test can accurately identify tuberculosis (TB) among patients with varying degrees of exposure. The method uses a high-sensitivity biosensor to detect a specific bacterial marker, potentially offering a diagnostic alternative for patients who cannot provide sputum.
Tuberculosis is typically diagnosed by assessing samples of a patient’s sputum, which are mucus secretions coughed up from the lungs and airways. However, many patients, especially those in the early stages of the disease or with a low bacterial burden, are unable to produce these samples.
“Every week of delay in diagnosing TB matters—so early identification may allow treatment to begin sooner and potentially reduce transmission,” says Sheng-Wei Pan, a physician in the department of chest medicine at Taipei Veterans General Hospital in Taiwan and the study’s lead author, in a release.
According to the World Health Organization, approximately one-quarter of the global population is infected with tuberculosis bacteria, and 5% to 10% of those individuals will develop active disease.
The research team evaluated a blood marker produced by the bacteria called 6-kDa early secreted antigenic target (ESAT-6). While this marker has been studied previously, most existing sensors lack the sensitivity required to distinguish active pulmonary tuberculosis from latent infection, exposure, or other lung diseases. Dr Pan and the research team used a new biosensor to achieve “highly sensitive quantification of circulating ESAT-6,” says Pan, in a release.
In a study of 217 patients, researchers quantified ESAT-6 levels in blood samples from individuals with active infections and a control group. The control group included patients with lung cancer, infections caused by other Mycobacterium species, latent tuberculosis, and healthy individuals with no known exposure.
The results showed a stepwise increase in the blood concentration of the marker across the spectrum of infection. The lowest levels were found in uninfected people, medium amounts in those with latent infections, and the highest levels in patients with active tuberculosis. This association remained strong even after accounting for factors such as age, sex, and the presence of diabetes.
Unlike other biomarkers that measure the body’s immune response to an infection, ESAT-6 is derived directly from the bacteria. Researchers believe this direct derivation allows the marker to perform better in identifying active disease than common blood-based alternatives.
While sputum cultures remain essential for verifying tuberculosis and identifying drug resistance, ESAT-6 shows promise as a tool for triaging patients when sputum-based diagnostics are limited or delayed. The research team is currently planning a prospective study to evaluate the use of this marker in real-world clinical settings, according to the study authors.
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