Asthma affects hundreds of millions of people worldwide, and tens of millions of people in the United States alone. However, new Canadian research suggests that a significant number of asthma cases may be falsely diagnosed.
Asthma is a chronic illness affecting the bronchial tubes, which normally allow air to come in and out of the lungs.
Worldwide, the condition affects approximately 300 million people. In the U.S., it is estimated that 1 in 12 people, or around 25 million individuals, live with the condition.
However, a new study, published in JAMA, suggests that the condition may be overdiagnosed.
Researchers - led by Dr. Shawn Aaron, respirologist at The Ottawa Hospital and a professor at the University of Ottawa in Canada - examined 613 patients selected randomly from 10 Canadian cities between January 2012 and February 2016.
The researchers recruited adults who reported being diagnosed with asthma in the 5 years leading up to the study.
Aaron and team re-evaluated the participants to see if they could confirm current asthma. They used a home peak flow meter, spirometry, and serial bronchial challenge tests to monitor the symptoms.
Over 33 percent of patients diagnosed with asthma did not have it
The study found that a large number of the participants might have initially received a false diagnosis. Furthermore, the vast majority of those whose asthma was not confirmed by the new study stopped taking their medication and were able to live safely without it for a year.
Researchers ruled out asthma in 203 of the 613 patients, which makes up 33.1 percent of the entire sample.
Of these, 12 study participants had other serious cardiorespiratory illnesses that might have been incorrectly diagnosed as asthma.
Additionally, 80 percent of the misdiagnosed patients had been taking asthma medication, and 35 percent of them had been doing so daily.
Patients who were deemed to be asthma-free showed no signs of acute worsening of asthma symptoms and no evidence of reversible airflow obstruction or bronchial hyperresponsiveness, even after they stopped taking the medication. The participants were examined by a study pulmonologist.
Of the participants whose asthma was not confirmed, 28 percent had no respiratory condition whatsoever, while the majority had minor issues, such as allergies or heartburn.
Aaron and team followed up on the 203 patients for 12 months. During this time, they gradually reduced the medication of the patients who were taking it daily over four study visits.
Over 90 percent of the misdiagnosed patients were able to safely stop taking the medications for a year.
"It is 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 did not need - medication that is expensive and can have side effects."
Dr. Shawn Aaron
The authors acknowledge two possible causes for the inability to confirm the asthma diagnosis in over 33 percent of the participants. One potential cause is the fact that asthma tends to clear itself up spontaneously - which the authors suggest might have occurred in 11.8 percent of the cases - while the other reason could simply be an initial misdiagnosis.
The study also revealed that upon the first diagnosis, over 49 percent of the patients were not subjected to objective testing procedures, such as serial peak flow testing, bronchial challenge testing, or spirometry.
"Doctors would not diagnose diabetes without checking blood sugar levels, or a broken bone without ordering an X-ray," says Dr. Aaron. "But for some reason, many doctors are not ordering the spirometry tests that can definitely diagnose asthma."
Dr. Aaron goes on to emphasize the need for public health education on how to properly diagnose asthma.
"We need to educate physicians and the public to get the diagnosis right in the first place. 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."
"Similarly," he add, "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."