A third of people recently diagnosed with asthma do not actually have the condition, research suggests.
Some people may be misdiagnosed with asthma while others may just have asthma that is no longer active, a new study found.
Experts led by a team at University of Ottawa carried out detailed breathing tests on 613 patients from 10 Canadian cities. All had been diagnosed with asthma in the past five years and every patient underwent a consultation with a lung specialist.
The findings showed that 33% of patients did not have active asthma. More than 90% were able to stop their asthma medications and remained safely off medication for a year.
Dr Shawn Aaron, lead author and respirologist at the Ottawa Hospital and professor at the University of Ottawa, said: “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impossible to say how many of these patients were originally misdiagnosed with asthma, and how many have asthma that is no longer active.
“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.”
Overall, eight out of 10 patients who did not have asthma had been taking medication for it, while 35% took it every day.
The most common form of asthma medication is an inhaler but some people also need to take tablets. Side-effects of some of the medication, such as steroids, include high blood pressure, stomach upsets and lower resistance to infection.
The study also found that of those patients originally diagnosed with asthma, almost half (49%) had not undergone the required airflow tests, known as spirometry, to ensure the diagnosis was correct.
Instead, doctors had used their own observations and the patient’s description of their symptoms to make a diagnosis.
Spirometry measures how much air you can breathe out in one forced breath.
Those patients found not to have asthma most often had other conditions instead. These included allergies or heartburn, while 28% had nothing wrong with them at all. Some 2% had serious conditions such as high blood pressure or heart disease.
Dr Aaron said: “Doctors wouldn’t diagnose diabetes without checking blood sugar levels, or a broken bone without ordering an X-ray.
“But for some reason, many doctors are not ordering the spirometry tests that can definitely diagnose asthma.
“It wasn’t a surprise to most patients when we told them they didn’t have asthma.
“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.”
The study was published in the Journal of the American Medical Association (JAMA).