Last Updated: 2009-12-11 19:30:25 -0400 (Reuters Health)

NEW YORK (Reuters Health) – Electric noses can sniff out the difference between chronic obstructive pulmonary disease (COPD) and asthma, new research shows.

Exhaled air from COPD and asthma patients showed distinct molecular profiles of volatile organic compounds (VOC), analyzed in real time by an "electronic nose," a handheld device that collects and analyzes expired breath. The electric results were repeatable and reproducible, according to the study, which is published in the December issue of the American Journal of Respiratory and Critical Care Medicine.

"Our data demonstrate a potential of electronic noses in the differential diagnosis of obstructive airway diseases and in the risk assessment in asymptomatic smokers," Dr. Niki Fens of the University of Amsterdam and colleagues write.

Differential diagnosis of the two conditions can be difficult due to their clinical and physiological similarities, Dr. Fens and colleagues note. They tested whether "breathprints" made by profiling VOCs in patients’ breath with an electronic nose might help in distinguishing between COPD and asthma.

The electric nose uses an array of nanosensors that react to various fractions of VOC in the breath, which are combined to create a specific "breathprint" that is then compared with a breathprint developed for a disease.

The researchers enrolled 30 COPD patients, 20 asthma patients, 20 non-smoking controls, and 20 smoking controls in the study.

COPD and asthma were "very well distinguished" by the breathprint technique, with a cross-validated accuracy value of 96 percent, the researchers found.

Asthma patients’ breathprints could also be distinguished from nonsmoking and smoking controls (95 percent and 93 percent, respectively; p < 0.0001). There was some overlap between the breathprints of COPD patients and the smoking controls, which "may be reflective of the presence of future patients with COPD among the ‘healthy’ smokers, who are still asymptomatic with a normal lung function," the researchers write.

The findings suggest electronic noses could be "an appealing alternative to metabolomic analysis of exhaled breath condensate, which requires highly sensitive laboratory assays," Fens and colleagues write. "Our results warrant the next step in the validation of the eNose for the diagnostic assessment of COPD and asthma by strictly following the STARD guidelines to test the diagnostic accuracy."

Am J Respir Crit Care Med 2009;180:1076-1082.