Researchers at Karolinska Institutet, in collaboration with colleagues in South Africa, have investigated whether tuberculosis can be traced in exhaled air. The results, published in the scientific journal Open Forum Infectious Diseases, show that a new method may help identify people with infectious tuberculosis directly in primary care.
Tuberculosis is an airborne disease that is often diagnosed by analysing sputum - mucus coughed up from the lungs. However, not all patients are able to produce sputum, which makes detection more difficult. In a new study, researchers tested whether DNA from the tuberculosis bacterium could be detected in exhaled air - known as aerosols - in people seeking care for respiratory symptoms.
The study was conducted at primary care clinics in South Africa and included 137 adult participants with tuberculosis. The researchers used a new device, TB Hotspot detectOR (THOR), which collects aerosols using electrostatic sampling. The samples were analysed using the same technique as for sputum, Xpert MTB/RIF Ultra.
The results show that the method was able to detect tuberculosis DNA in exhaled air in 47 per cent of those who had a positive sputum test. Among those with high levels of bacteria in sputum, the sensitivity was slightly higher at 57 per cent. At the same time, the specificity - the ability to correctly identify those without the disease - was 77 per cent.
"It is promising that we can detect infectious tuberculosis directly in the air, especially in settings where sputum samples are difficult to obtain," says Jay Achar, researcher at the Department of Global Public Health at Karolinska Institutet.
The study also found that certain factors increased the likelihood of detecting tuberculosis DNA in aerosols. This was particularly true for men with high bacterial levels in sputum. Conversely, people with fever were slightly less likely to test positive in air samples.
"This is a first step towards understanding how tuberculosis is transmitted and how we can identify infectious individuals earlier," says Jay Achar.
The researchers also noted that DNA from the tuberculosis bacterium was found in 30 per cent of environmental samples taken in the clinic setting, despite thorough cleaning. This suggests that the method is sensitive but also highlights potential risks of transmission in healthcare environments.
The study was conducted in collaboration with researchers at Stellenbosch University in South Africa. No conflicts of interest have been reported.
Publication
Jay Achar, Rouxjeane Venter, Jamie van Schalkwyk, Zandile Booi, Zama Mahlobo, Zaida Palmer, Nuno Rufino de Sousa, Knut Lönnroth, James A Seddon, Antonio Gigliotti Rothfuchs, Grant Theron, Detection of aerosolized, Open Forum Infectious Diseases, 2025
