JAN 24, 2017 2:05 PM PST

One-Third of Asthma Patients are Misdiagnosed


About one in 12 Americans, or 25 million people, are diagnosed with asthma. But a new study reports that about a third of those people are misdiagnosed, and may be taking asthma medication unnecessarily.

Asthma is a chronic respiratory condition marked difficulty breathing, coughing, wheezing, and shortness of breath. These symptoms are brought on by the airway swelling up and producing extra mucus in response to different types of allergens. Patients diagnosed with asthma take long-term medications like inhaled corticosteroids, and may also have to carry fast-acting rescue medications in case of a serious asthma attack.

However, recent studies suggest that not all patients diagnosed with asthma actually have asthma. The current study expanded on this by studying over 600 patients diagnosed with asthma in the past five years in Canada. To confirm whether the patients truly have asthma, the scientists used a series of tests including at home peak flow meter, spirometry, and serial bronical challenge tests.

They found that a third of the patients diagnosed with asthma did not, in fact, have active asthma.

"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impossible to say how many of these patients were originally misdiagnosed with asthma, and how many have asthma that is no longer active," said Dr. Shawn Aaron, senior scientist and respirologist at The Ottawa Hospital and professor at the University of Ottawa, and the study’s senior author.

"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." Aaron and his team reported that 90 percent of the patients reclassified as not having asthma were able to stop taking their asthma medication without adverse effects.

The team also found that many patients had already suspected a misdiagnosis all along. "It wasn't a surprise to most patients when we told them they didn't have asthma," said Dr. Aaron. "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."

In the 33 percent of patients that didn’t seem to have asthma, Aaron’s team found that the majority didn’t actually have anything medically wrong. In some, the problem seemed minor, like allergies or heartburn.

So why does asthma have such a high instance of overdiagnosis? In looking through the records of how patients were diagnosed, Aaron’s team discovered something else alarming. It seems 49 percent of patients were diagnosed without evidence from airflow tests required by medical guidelines. Doctors seemed to rely more on the patient’s chief complaints and their own observations.

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

"We need to educate physicians and the public to get the diagnosis right in the first place," said Dr. Aaron. "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). Similarly, if patients think they may have been misdiagnosed with asthma or that they no longer have asthma, they should ask their doctor for a spirometry test. Asthma can be deadly, so patients should never go off their medication without speaking to a doctor first."

Additional sources: MNT, Ottowa Hospital Research Institute

About the Author
  • I am a human geneticist, passionate about telling stories to make science more engaging and approachable. Find more of my writing at the Hopkins BioMedical Odyssey blog and at TheGeneTwist.com.
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