Study finds over 30% adult asthma diagnoses are incorrect

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A study has found that 33% of adults recently diagnosed with asthma by their physicians did not have active asthma. Over 90% of these patients were able to stop their asthma medications and remain safely off medication for one year.

“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impossible to say how many of these patients were originally misdiagnosed with asthma, and how many have asthma that is no longer active,” said lead author of the study Dr Shawn Aaron, senior scientist and respirologist at The Ottawa Hospital and professor at the University of Ottawa. “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.” 80% of the participants who did not have asthma had been taking asthma medication, and 35% took it daily.

The study also found that doctors often did not order the tests needed to confirm an asthma diagnosis. Instead they based their diagnosis solely on the patient’s symptoms and their own observations.

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

The study looked at 613 randomly selected patients from 10 Canadian cities diagnosed with asthma in the last five years. After a series of detailed breathing tests followed by consultation with a lung specialist, asthma was ruled out in a third of these patients.

The research team was able to access the medical records of 530 of the patients to see how they were originally diagnosed. They found that in 49% of these cases, physicians had not ordered the airflow tests required by medical guidelines.

When the patients that were found not to have asthma were re-diagnosed, most had minor conditions like allergies or heartburn, and 28% had nothing wrong with them at all – 2% had serious conditions like pulmonary hypertension or heart disease that had been misdiagnosed as asthma, and went on to receive proper treatment.

“It wasn’t a surprise to most patients when we told them they didn’t have asthma,” said 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.”

This study confirms and expands on earlier findings of Aaron’s, which suggested that 30% of asthma patients had been misdiagnosed.

“We need to educate physicians and the public to get the diagnosis right in the first place,” said 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.”

Abstract
Importance: Although asthma is a chronic disease, the expected rate of spontaneous remissions of adult asthma and the stability of diagnosis are unknown.
Objective: To determine whether a diagnosis of current asthma could be ruled out and asthma medications safely stopped in randomly selected adults with physician-diagnosed asthma.
Design, Setting, and Participants: A prospective, multicenter cohort study was conducted in 10 Canadian cities from January 2012 to February 2016. Random digit dialing was used to recruit adult participants who reported a history of physician-diagnosed asthma established within the past 5 years. Participants using long-term oral steroids and participants unable to be tested using spirometry were excluded. Information from the diagnosing physician was obtained to determine how the diagnosis of asthma was originally made in the community. Of 1026 potential participants who fulfilled eligibility criteria during telephone screening, 701 (68.3%) agreed to enter into the study. All participants were assessed with home peak flow and symptom monitoring, spirometry, and serial bronchial challenge tests, and those participants using daily asthma medications had their medications gradually tapered off over 4 study visits. Participants in whom a diagnosis of current asthma was ultimately ruled out were followed up clinically with repeated bronchial challenge tests over 1 year.
Exposure: Physician-diagnosed asthma established within the past 5 years.
Main Outcomes and Measures: The primary outcome was the proportion of participants in whom a diagnosis of current asthma was ruled out, defined as participants who exhibited no evidence of acute worsening of asthma symptoms, reversible airflow obstruction, or bronchial hyperresponsiveness after having all asthma medications tapered off and after a study pulmonologist established an alternative diagnosis. Secondary outcomes included the proportion with asthma ruled out after 12 months and the proportion who underwent an appropriate initial diagnostic workup for asthma in the community.
Results: Of 701 participants (mean [SD] age, 51 [16] years; 467 women [67%]), 613 completed the study and could be conclusively evaluated for a diagnosis of current asthma. Current asthma was ruled out in 203 of 613 study participants (33.1%; 95% CI, 29.4%-36.8%). Twelve participants (2.0%) were found to have serious cardiorespiratory conditions that had been previously misdiagnosed as asthma in the community. After an additional 12 months of follow-up, 181 participants (29.5%; 95% CI, 25.9%-33.1%) continued to exhibit no clinical or laboratory evidence of asthma. Participants in whom current asthma was ruled out, compared with those in whom it was confirmed, were less likely to have undergone testing for airflow limitation in the community at the time of initial diagnosis (43.8% vs 55.6%, respectively; absolute difference, 11.8%; 95% CI, 2.1%-21.5%).
Conclusions and Relevance: Among adults with physician-diagnosed asthma, a current diagnosis of asthma could not be established in 33.1% who were not using daily asthma medications or had medications weaned. In patients such as these, reassessing the asthma diagnosis may be warranted.

Authors
Shawn D Aaron; Katherine L Vandemheen; J Mark FitzGerald; Martha Ainslie; Samir Gupta; Catherine Lemière; Stephen K Field; R Andrew McIvor; Paul Hernandez; Irvin Mayers; Sunita Mulpuru; Gonzalo G Alvarez; Smita Pakhale; Ranjeeta Mallick; Louis-Philippe Boulet for the Canadian Respiratory Research Network

University of Ottowa material
JAMA abstract


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