Overdiagnosis of asthma in Canadian communities

Asthma is overdiagnosed in an estimated 30 percent of Canadian adult , according to a study presented at the ATS 2016 International Conference.

"Careful testing revealed that 33 percent of people who had been recently diagnosed with asthma in the community did not have current asthma even after withdrawal of asthma medications," said lead study author Shawn Aaron, MD, of the Ottawa Hospital Research Institute, Ottawa.

The prospective multicenter study randomly recruited 701 adult nonsmoking participants from 10 Canadian communities, who reported a history of physician-diagnosed asthma in the previous 5 years. Investigators obtained information to determine how a diagnosis of asthma was originally made. Spirometry, home peak flow, and symptom monitoring, as well as repeated bronchial challenge tests, were used to assess participants. They were also tapered off of asthma medications over four study visits.

Of the 701 participants, 613 were conclusively assessed with an asthma diagnosis. The participants in whom an asthma diagnosis was not confirmed had no evidence of airflow obstruction or bronchial hyper-reactivity or acute asthma worsening despite tapering off all asthma medications. Participants with no evidence of asthma were sent to pulmonologists and followed for one year.

"Pulmonologists diagnosed alternative diagnoses instead of asthma in 87 percent of these subjects," the study authors wrote. "Results to date indicate that 81 percent in whom asthma was excluded did not restart asthma medications nor require healthcare utilization for asthma during the subsequent 12-month follow up period."

Only half of participants received spirometry at the time of their initial asthma diagnosis, according to the study authors.