Asthma was ruled out in 33% of adults in the general Canadian population who had been diagnosed by a physician during the preceding 5 years, according to a report published online Jan. 17 in JAMA.

In a prospective multicenter cohort study involving 613 asthma patients, 203 had no evidence of current asthma when they underwent serial assessments of respiratory symptoms, lung function, and bronchial provocation testing while not taking asthma medications. More than 90% of these 203 participants safely refrained from using the medications for an additional 1-year follow-up period, said Shawn D. Aaron, MD, of Ottawa (Ont.) Hospital Research Institute, and his associates in the Canadian Respiratory Research Network.

Some of these patients were likely misdiagnosed initially and some likely experienced remission since their initial diagnosis. Either way, reassessing asthma diagnoses may be warranted in many patients, the investigators said ( JAMA 2017;317[3]:269-79 ).

To assess whether some patients could safely discontinue asthma medications because they no longer had the disease, the researchers performed a random sampling of the general adult population (approximately 17,000 people) living in urban, suburban, or rural areas in and around the 10 largest cities in Canada during a 3-year period. Those who reported that a member of the household had been diagnosed as having asthma within the previous 5 years were invited to participate in the study.

A total of 613 men and women (mean age, 51 years) completed the study, undergoing spirometry to assess airflow obstruction, methacholine challenges to assess airway hyperresponsiveness, clinical examination by a pulmonologist, and, if indicated, tapering and discontinuation of asthma medications. Those in whom asthma was ruled out were closely followed for 1 year, undergoing repeat bronchial challenge testing and reporting any worsening of asthma signs and symptoms.

At baseline, 87% of the participants said that they had recently used asthma medications and 45% said they used such medications daily. The remainder had already stopped using asthma medications, an indication that many patients can tell when their asthma has remitted (or was never present) and may adjust their medication use with or without a physician’s guidance, Dr. Aaron and his associates said.

Current asthma was confirmed in 62.3% of the study participants. The primary study outcome – the proportion of patients in whom a current asthma diagnosis was ruled out – was 33.1%, or 203 patients. Only 44% of these participants who did not have current asthma had undergone objective testing before their initial diagnosis, compared with 56% of patients in whom asthma was confirmed. This indicates that “whenever possible, physicians should order objective tests, such as prebronchodilator and postbronchodilator spirometry, serial peak flow measurements, or bronchial challenge tests, to confirm asthma at the time of initial diagnosis,” the investigators said.

A total of 35% of the participants in whom asthma was ruled out had been using daily asthma medications. “Use of asthma medications in these patients presumably provided only risks for medication adverse effects and cost, with little opportunity for therapeutic benefit,” the researchers noted. Twelve patients – 2% of the study population – were found to have serious cardiorespiratory conditions that had been misdiagnosed as asthma: four people with ischemic heart disease (two requiring percutaneous coronary intervention), two with subglottic stenosis (both requiring airway dilation procedures), two with bronchiectasis, and one each with interstitial lung disease, pulmonary hypertension, sarcoidosis, and tracheobronchomalacia.

During the additional year of follow-up, 22 of the 203 patients in whom asthma had been ruled out had a positive bronchial challenge test result at 6 or 12 months. Six resumed using asthma medications, one was treated with a brief course of oral corticosteroid, and the others did not require asthma medications.

The Canadian Institutes of Health Research supported the study. Methapharm provided provocholine and Trudell Medical International provided the peak flow meters used in the study. Dr. Aaron reported having no relevant financial disclosures; his associates reported ties to numerous industry sources.