One-third of Adults Diagnosed with Asthma Don't Have the Disease, Canadian Study Finds

A new research study revealed that 33 percent of adults in Canada who were diagnosed with asthma in the last five years do not have active asthma after all.

The study, “Re-evaluation of Diagnosis in Adults With Physician-Diagnosed Asthma,” was published in the Journal of the American Medical Association.

Lead author of the study was Dr. Shawn Aaron, a senior scientist and respirologist at Ottawa Hospital in Canada. In 2008 he had suggested that about 30 percent of asthma patients had been misdiagnosed. These findings confirm his suspicions.

Of the 613 randomly selected patients from 10 Canadian cities who participated in the study, 33 percent were found to not have asthma. Of those patients, about 90 percent were able to stop their medication and stay off it for at least one year with no threat to their health.

The team concluded that 80 percent of the patients who didn’t have asthma had been taking medication unnecessarily for over a year, and 35 percent of them had been taking medication every day.

“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impossible to say how many of these patients were originally misdiagnosed with asthma, and how many have asthma that is no longer active,” Aaron said in a press release. “What we do know is that they were all able to stop taking medication that they didn’t need – medication that is expensive and can have side effects.”

“Doctors wouldn’t diagnose diabetes without checking blood sugar levels, or a broken bone without ordering an x-ray,” he said. “But for some reason many doctors are not ordering the spirometry tests that can definitely diagnose asthma.”

To determine how these study participants had been diagnosed in the first place, investigators looked at all the medical records of patients they could access (530 in total). They found that in 49 percent of the cases, physicians had not ordered the airflow tests needed to confirm a diagnosis and had based their decision on their own observations and their patients’ self-reported symptoms.

In total, 28 percent of the participants did not have anything wrong with their health, and only 2 percent actually suffered from a serious condition like pulmonary hypertension or heart disease. Patients found to be disease-free stopped taking their asthma medication, while the remaining patients began taking the correct medicine right away.

“It wasn’t a surprise to most patients when we told them they didn’t have asthma,” Aaron said. “Some knew all along that their puffer wasn’t working, while others were concerned that they might have something more serious. Thankfully, the majority of the conditions were mild and easily treated.”

“We need to educate physicians and the public to get the diagnosis right in the first place,” he added. “Patients who have difficulty breathing should ask their doctor to order a breathing test (spirometry) to determine if they might have asthma or even chronic obstructive pulmonary disease (COPD).”

And, if patients think they may have been misdiagnosed or no longer have the disease, they should ask their doctor for a spirometry test, he said. “Asthma can be deadly, so patients should never go off their medication without speaking to a doctor first,” Aaron said.