Tuberculosis (TB) is an airborne disease that remains one of the world's deadliest infections, primarily diagnosed through sputum analysis. However, many patients cannot produce sputum, making detection and timely treatment difficult, especially in primary care settings. Now, researchers testing whether DNA from the tuberculosis bacterium could be detected in exhaled air have found that the method can identify infectious individuals directly in primary care settings.

The study, conducted by researchers at Karolinska Institutet (Stockholm, Sweden) in collaboration with Stellenbosch University (Cape Town, South Africa), involved 137 adult participants with tuberculosis symptoms who were recruited from primary care clinics in South Africa. They used a device called TB Hotspot detectOR (THOR), which was developed at Karolinska Institutet, to collect aerosols from exhaled breath through electrostatic sampling. The samples gathered with the device were analyzed using the Xpert MTB/RIF Ultra technique, the same molecular method commonly used to detect TB in sputum.

The results, published in Open Forum Infectious Diseases, showed that tuberculosis DNA was detected in exhaled air in 47% of participants who tested positive via sputum analysis. Among those with high bacterial loads in sputum, sensitivity rose slightly to 57%, while the specificity—indicating correct identification of uninfected individuals—was 77%. The study also found that bacterial DNA appeared in 30% of environmental samples taken in the clinic, suggesting the method's sensitivity and the potential for airborne transmission in healthcare environments.

The study provides a foundation for developing non-invasive TB screening tools that can detect infection in individuals unable to produce sputum. Identifying infectious cases directly through exhaled air could transform diagnosis, reduce transmission, and improve control of TB in high-burden regions where sputum samples are difficult to obtain. The researchers emphasize that this is an early step toward understanding transmission dynamics and developing rapid, accessible diagnostics for global use in primary healthcare settings.

“It is promising that we can detect infectious tuberculosis directly in the air, especially in settings where sputum samples are difficult to obtain,” said Jay Achar, co-author of the study. “This is a first step towards understanding how tuberculosis is transmitted and how we can identify infectious individuals earlier.”

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