Asthma Misdiagnosed in One-Third of Cases: Study

New research suggests that about one out of every three adults diagnosed with asthma are later found to not have the disease, raising concerns about potentially unnecessary treatments. 

In a study published this week in the Journal of the American Medical Association (JAMA), Canadian researchers indicate that about one-third of patients discovered that asthma was misdiagnosed five years later, and had no signs of the condition during follow-up testing.

Researchers analyzed 700 randomly selected adults with asthma, diagnosed by a doctor in 10 Canadian cities from January 2012 to February 2016. Adults had the asthma diagnosis within the past five years and 613 patients were fully eligible for the study.

During the study, asthma diagnosis was ruled out in 203 of the 613 study participants, revealing 33% of patients did not have asthma after being diagnosed with asthma by a doctor. Those patients had undergone repeated bronchial challenge tests over one year and were still found not to have asthma, revealing the misdiagnosis.

Twelve months following that, participants in the study were followed up with again and 181 patients, or 30 percent, still exhibited no clinical or laboratory evidence of asthma.

Twelve patients were found to have serious cardiorespiratory conditions that were misdiagnosed as asthma by their doctors.

Information from the doctor on how the diagnosis was made was obtained for the study. Any patients who used long term oral steroids or were unable to be tested using spirometry, measuring lung function through inhalations, were excluded from the study.

Patients were assessed with home monitoring, symptom monitoring and bronchial challenge tests. Patients using daily asthma medications had their medications gradually tapered off over four study visits to see how well their lung function was without the medications.

Using those methods, 33% of patients did not have a true diagnosis of asthma. Study authors said some patients were a clear misdiagnosis and others may have experienced remission of their asthma.

Researchers did indicate patients who had asthma ruled out were less likely to have undergone testing for airflow limitation by their doctor at the time of initial diagnosis compared to confirmed asthma sufferers.

Study authors say it is possible for patients to test negative for asthma and still exhibit symptoms or to be diagnosed incorrectly. They note that asthma is a complicated disease, and conditions like acid reflux and vocal cord dysfunction syndrome can have similar symptoms, like wheezing, cough, chest pain, and difficulty breathing.