SAN DIEGO – Researchers in England used a novel gas analysis technique to detect tuberculosis in the breath, with a sensitivity of 93% and a specificity of 94%.
“Clearly these are promising results,” Dr. Amandip Sahota said at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy. “What interested me the most is that we were able to detect a significant difference in chemicals in both pulmonary and extra-pulmonary TB, which did indicate to us that the disease does not need to be limited to the lungs to be detectable in the breath.”
According to the latest data from the World Health Organization, there were 9 million active TB cases and 1.5 million deaths from the disease in 2013. Of these deaths, 80,000 were in children.
“TB remains a diagnostic challenge well into the 21st Century,” said Dr. Sahota, a consultant physician in infectious diseases at University Hospitals of Leicester, England. “We are still heavily reliant on the standard culture, which is both slow and resource-intensive throughout the world. Despite the advent of TB-PCR, we are still far away from a diagnostic test which is both available at point of care, at low cost, and is available throughout the world.”
In a study he conducted during his time as a research fellow at the University Hospitals of Coventry, in association with colleagues at the University of Warwick, Dr. Sahota and his associates used a field asymmetric ion mobility spectrometry device to collect samples of exhaled breath from 25 patients with suspected pulmonary or extra-pulmonary TB over a period of 6 months, before or within 1 week of treatment. For comparison, exhaled breath from 19 healthy controls was also obtained.
While ion mobility spectrometry has been used for years by the military and the security industry to detect explosives, for example, the technology has more recently been used to help diagnose medical conditions ranging from cancers to infections.
“Breath testing for TB is not new, but what is very exciting is the advent of newer gas sensor technologies which are being developed in line with a clinical need,” Dr. Sahota explained. “The point of interest here is volatile organic compounds: chemicals which are gaseous at ambient temperatures, often produce odors, and are endogenous products of metabolism in both health and disease states. So testing for breath can be quick, easy, and noninvasive. Clearly there’s plenty of sample. It’s rapid, and it allows access to chemicals in the blood, which are visible in the breath through ventilator processes.”
Patients in the study, which is believed to be the first of its kind, breathed into a 3L Tedlar air sample bag and the samples were tested within 2 hours with a portable field asymmetric ion mobility spectrometry device made by Oxford Immunotec, Inc. After measuring the ionic mobility of volatile organic compounds in the headspace, the researchers determined that the test was highly effective in detecting TB in the breath, with a sensitivity of 93% and a specificity of 94%.
“Clearly this is a small study and we do need to repeat this in a larger cohort to validate it further,” Dr. Sahota said. “We also need to investigate potential confounders such as other comorbidities and medications. Ideally, we’d like to use a smaller, more portable instrument which is ideally hand-held, so we’re exploring commercial partnerships.”
The study was funded by the Medical Research Council. The researchers reported having no financial disclosures.
*This story was updated on 10/5/2015.