Hundreds of thousands of Canadian asthma patients may not have the condition after all, based on the findings of a recent study that retested patients across the country.

In Monday's online issue of the Canadian Medical Association Journal, Dr. Shawn Aaron of the Ottawa Health Research Institute and his colleagues looked at 496 adults from eight Canadian cities — Vancouver, Calgary, Winnipeg, Hamilton, Ottawa, Montreal, Quebec and Halifax — who received a diagnosis of asthma from a physician.

'If it hadn't been for this asthma study what would have happened to me? I'd still be taking inhalers.'— Suzanne Abou-Hamda

When participants were retested using clinical guidelines, 30 per cent had no evidence of the chronic disease, the researchers found.

When Suzanne Abou-Hamda of Ottawa was pregnant with her four-year-old son, her doctor blamed her persistent cough on asthma. She lived in fear of an asthma attack, and got rid of the family cat for fear its dander would aggravate the condition.

But Abou-Hamda was one of the trial participants who turned out not to have asthma after all.

"I felt very happy but also very angry because as I said, I don't think it's a very harmless drug I was taking," she said. "If it hadn't been for this asthma study, what would have happened to me? I'd still be taking inhalers."

Aaron said he was astounded by the results, noting that the prevalence of asthma in Canada and the U.S. has increased by 75 per cent between 1980 and 1994, after adjusting for age.

Consider test results in diagnosis, researchers urge doctors

Like Abou-Hamda, Aaron is concerned money is being spent unnecessarily on expensive asthma medications that expose patients unnecessarily to potential side-effects of inhaled steroids, such as osteoporosis, glaucoma and cataracts.

Overdiagnosis of asthma could also mask a more serious condition such as pulmonary hypertension, or bronchitis, Aaron said, blaming the overdiagnosis on the hassle factor of the clinical tests.

"Physicians are under a lot of pressure to manage a lot of patients quickly," Aaron said. "For a patient who comes in complaining of shortness of breath and wheeze, it's much more easy and it takes much less time to say, 'I think you have asthma, take this puffer.'"

It is dangerous to stop taking asthma medications abruptly, Aaron cautioned. If someone thinks their medications aren't helping, then together with their physician, they should consider tapering off, if repeated lung function tests and symptoms suggest it is safe, he said.

"Physicians should consider objective testing using spirometry and, if necessary, bronchial challenge testing to confirm asthma in patients with respiratory symptoms," the researchers wrote.

Making test routine for family doctors

At a minimum, asthma patients who have never had one should ask for spirometry tests, in which they blow through a tube to measure the rate and volume of airflow through the lungs, the study's authors said.

There is no reason for spirometry tests not to be routine in primary care, just as using a blood pressure cuff is, Dr. Matthew Stanbrook, the journal's deputy scientific editor and Dr. Alan Kaplan, chair of the Family Physicians Airways Group of Canada in Edmonton, wrote in a commentary accompanying the study.

The testing equipment costs more than $2,000, Aaron said, and training is also needed to administer the test correctly.

Doctors could also ask laboratories to fax uninterpreted results before waiting for the official report and participate in mentoring and continuing education programs to interpret spirometry results, the journal editors suggested.

Abou-Hamda said in her case, her life has changed for the better after participating in the study, although she can't have her cat back.