Washington: As many as one third of adults diagnosed with asthma may not actually have the disease, according to a Canadian study.
The study, published in the Journal of the American Medical Association on Tuesday, looked at 613 randomly selected patients from 10 Canadian cities diagnosed with asthma in the last five years, Xinhua news agency reported.
After a series of detailed breathing tests followed by consultation with a lung specialist, asthma was ruled out in 203 or 33 per cent of these patients.
According to the study, 181 participants or 30 per cent continued to exhibit no clinical or laboratory evidence of asthma after an additional 12 months of follow-up.
The researchers speculated that the failure to confirm a previous diagnosis of asthma by doctors could be because of spontaneous remission or misdiagnosis.
"It's impossible to say how many of these patients were originally misdiagnosed with asthma, and how many have asthma that is no longer active," lead author Shawn Aaron, senior scientist and respirologist at Ottawa Hospital and professor at the University of Ottawa, said in a statement.
According to the study, 80 per cent of the participants who did not have asthma had been taking asthma medication, and 35 per cent took it daily.
The study also found that doctors often did not order the tests needed to confirm an asthma diagnosis. Instead they based their diagnosis solely on the patient's symptoms and their own observations.
"We need to educate physicians and the public to get the diagnosis right in the first place," said Aaron. "Asthma can be deadly, so patients should never go off their medication without speaking to a doctor first."
Diagnosis of asthma can be difficult because various types have been identified, all of which potentially have different triggers and symptoms.
Asthma can be episodic or can follow a relapsing and remitting course, which further complicates attempts to arrive at a diagnosis based on a single patient-physician encounter.