ATS: 'Electronic Nose' Sniffs Out Asthma

SAN FRANCISCO, May 25 -- The electronic nose, already proficient at sniffing out bombs and optimizing coffee roasting, may become a one-stop diagnostic tool for asthma.

The Cyranose device detected patterns in exhaled volatile gases that were able to distinguish asthmatic patients from controls in a pilot study presented here at the American Thoracic Society meeting.

The device was less effective at discriminating asthma severity, reported Silvano Dragonieri, M.D., of Leiden University Medical Center in Holland, and colleagues.

If the findings hold up in prospective studies, it may be a step toward the long-sought simple test for an accurate asthma diagnosis, commented John Mastronarde, M.D., of Ohio State in Columbus, who moderated a press conference on the study.

"As we all know there is no single test for asthma," he said. "Asthma is a very heterogeneous disease?it's still a clinical diagnosis that is tough to do."

Previous studies have demonstrated proof of principle for the device in detecting tuberculosis bacteria and lung cancer from characteristic volatile gas patterns, so there was reason to hope that it could be taught to recognize asthma, Dr. Dragonieri said.

The handheld device contains of an array of 32 polymer sensors that reversibly bind to volatile organic compounds in air. Binding changes the electrical resistance of the polymer and is read out as a "smell print" by statistical pattern recognition learning software.

In the cross-sectional study, the researchers tested the breath of 10 patients with mild asthma, 10 with severe asthma, 10 young healthy controls ages 18 to 44, and 10 older healthy controls ages 45 to 75.

None of the subjects had ever been smokers. Controls had no history of asthma and no atopy.

Two breath samples were collected for each participant over a period of about 10 minutes.

Among the findings, the investigators reported:

• 100% cross validation in distinguishing mild asthma from young controls.
• 90% cross validation in distinguishing severe asthma from older controls.
• 65% cross validation in distinguishing mild and severe asthma.
• 50% cross validation in distinguishing young and older controls.
• 100% cross validation for reproducibility in distinguishing mild asthma from controls.
• 90% to 95% cross validation for reproducibility in distinguishing severe asthma from controls.

Dr. Dragonieri called the short-term reproducibility "adequate" and the overall results "promising."

"Volatile organic compound pattern analysis by electronic noses may become a realistic option in asthma diagnosis and monitoring," he said.

But first, external validation of the results is needed, he noted. The group plans to do a study prospectively testing patients with suspected but unconfirmed disease, he said.

In addition to non-invasive point-of-care testing possibilities, one of the electronic nose's most anticipated advantages would be in diagnosis of toddlers, which the research group is working toward, Dr. Dragonieri said.

"Clearly this is a small pilot study and there's a lot of work to be done in the future," Dr. Mastronarde said, but added, "There's a lot of potential here,"