The study involved 613 patients randomly selected from 10 Canadian cities between January 2012 and February 2016. Although all said they had been diagnosed with asthma, a “current asthma” diagnosis was ruled out in 203 study participants – or 33 per cent of the group. In follow-up testing after a year, 30 percent still showed no evidence of the respiratory disease.
“There are two reasons why patients don’t have current asthma,” says respirologist Dr. Shawn Aaron, who led the research. “Some were misdiagnosed to begin with. Others had it, but they are now in remission and their asthma is inactive.”
Reasons for Being Wrongly Diagnosed
Furthermore, 12 participants had serious cardio-respiratory conditions that had been wrongly diagnosed as asthma.
One of the problems is that doctors prescribe asthma medication based on symptoms such as wheezing, coughing or shortness of breath. These are common symptoms when the airways are restricted, and not exclusive to asthma. To make a proper diagnosis, patients need to take a series of lung function tests that measure airflow capacity.
That’s precisely what Aaron, a senior scientist at The Ottawa Hospital Research Institute, and his fellow researchers did for this study. Participants were assessed with home peak flow and symptom monitoring, spirometry, and serial bronchial challenge tests. Some were weaned off asthma medication.
Asthma is complex – it’s difficult to diagnose and some patients have periods of remission.
Patients: Ask for Spirometry
Aaron suggests that patients experiencing symptoms should ask for spirometry testing. If diagnosed with asthma, but later experiencing no symptoms such as shortness of breath or coughing, he would ask for reassessment.
Aaron is concerned that patients may be taking medications they don’t need, which can be expensive and can lead to side effects over time. As well, they may have a cardiac or pulmonary disease that has not been diagnosed.
He stresses he doesn’t want patients who suspect they’re wrongly diagnosed to simply stop taking their medications. “Go see your doctor, discuss it with them and ask for a spirometry test,” he says.
It’s estimated that 8 per cent of Americans, or around 25 million people, had asthma in 2009, according to the American Academy of Allergy, Asthma & Immunology. Statistics Canada states that about 8 per cent live with the condition.
View the study here.