New blood test may spot active TB without sputum

Clinical takeaway: A highly sensitive blood assay measuring circulating ESAT-6 may eventually serve as a triage test for suspected pulmonary TB when sputum collection is difficult or delayed. It is not yet ready to replace sputum culture or molecular testing, which remain necessary to confirm disease and assess drug resistance. These findings are conference-reported and have not yet been peer reviewed.

Earlier identification of active TB—particularly in patients unable to produce sputum—could accelerate treatment and reduce opportunities for transmission.

In a study presented at the Association for Diagnostics & Laboratory Medicine (ADLM) 2026 meeting, researchers evaluated a new biosensor that directly measures ESAT-6, a protein released by Mycobacterium tuberculosis, in blood. The analysis included 217 patients with active pulmonary TB or control conditions, including latent TB infection, TB exposure without infection, nontuberculous mycobacterial lung disease, lung cancer, and no known TB exposure.

Blood ESAT-6 concentrations rose stepwise across the TB spectrum: levels were lowest among exposed but uninfected participants, intermediate among those with latent infection, and highest among patients with active pulmonary TB. The marker differentiated TB from non-TB groups and outperformed 2 commonly used blood-based biomarkers, with the association remaining after adjustment for age, sex, and diabetes.

Unlike QuantiFERON-TB Gold Plus, which measures the patient’s interferon-gamma immune response and cannot distinguish latent infection from active disease, the investigational assay detects a component derived directly from TB bacteria. It could therefore complement current infection testing by helping identify which patients are more likely to have active disease and need urgent sputum-based evaluation.

“Every week of delay in diagnosing TB matters,” lead author Sheng-Wei Pan, MD, said, adding that earlier identification could allow treatment to begin sooner and potentially reduce transmission.

The findings require prospective validation because participants’ diagnoses were already known. Researchers are planning a real-world study to determine whether circulating ESAT-6 can reliably guide clinical triage.

Source: Association for Diagnostics & Laboratory Medicine (ADLM). (2026 July 28). New blood test for tuberculosis could reduce the spread of this top global infectious-disease killer