Many adults who believe they have asthma actually may not.

Using random dialing, Canadian researchers recruited 613 men and women who had been given a diagnosis of asthma within the past five years. Then over four visits they gave them a series of drug challenges and spirometry, a physical test of breathing capacity, to confirm or rule out the disorder. The study is in JAMA.

The researchers were able to rule out asthma in 203, or about a third of subjects, most of whom were taking asthma medicine. They tapered their medicine, and 181 of them showed no signs of asthma over a 15-month follow-up.

In about 2 percent of cases, the researchers found another breathing issue that may have been misdiagnosed as asthma. In about half of cases, the diagnosis was based on symptoms alone, with no objective laboratory testing. Spontaneous remission explained a number of other cases.

The lead author, Dr. Shawn D. Aaron, a professor of medicine at the University of Ottawa, said that a cough or a wheeze is not enough to diagnose asthma and put a person on inhaled steroids.

“If you have shortness of breath, wheeze or cough, you should suggest that the doctor order a spirometry test,” he said. “It’s a quick test with no risks or side effects that can predict asthma or other respiratory conditions.”