Many Canadians misdiagnosed as asthmatic: study

Tue Nov 18, 2008 12:50pm EST
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By David Ljunggren

OTTAWA (Reuters) - Up to 30 percent of Canadians diagnosed with asthma may not have the disease, and obese people are particularly vulnerable to misdiagnoses, according to a study released on Tuesday.

A team led by Dr. Shawn Aaron of the Ottawa Health Research Institute said doctors tempted to diagnose asthma should carry out more specialized tests such as spirometry, which involves breathing into a special machine to check lung function.

Aged-adjusted data showed that between 1980 and 1994 the number of people diagnosed with asthma had grown by 75 percent, in part due to increasing awareness by patients and their doctors, the Ottawa research team said.

But the study -- published in the Canadian Medical Association Journal -- suggests that at least part of the increase may reflect misdiagnoses.

The team carried out a six-month study of 496 obese and non-obese patients who had been diagnosed with asthma.

"We found that one-third of the participants who had received a diagnosis of asthma by a physician had no evidence of asthma when their medications were tapered and when they were evaluated with serial assessments of symptoms, lung function and bronchial challenge tests," it said.

"One obvious interpretation of this observation is that asthma was over-diagnosed in the community. Consequently, over-diagnosis and changes in diagnostic labeling may be contributing to increases in the prevalence of asthma reported in developed countries."

Asthma can be confused with other respiratory diseases as well as chronic obstructive pulmonary disease.   Continued...