By Salynn Boyles
One in three people with recent physician-diagnosed asthma did not have active asthma when evaluated using spirometry and serial bronchial challenge, results of a cohort study indicated, and more than 90% were able to stop treatment without harm.
About 44% of patients found not to have asthma had been diagnosed without the use of spirometry, bronchial challenge, or serial peak flow measurement, making it questionable whether they ever actually had asthma.
The study findings suggest that the common practice of diagnosing asthma in adults based on symptoms alone often leads to misdiagnosis, Shawn Aaron, MD, of Canada's University of Ottawa.
The multicenter cohort study, which followed adults in Canada with a recent diagnosis of asthma recruited through random telephone contact, was designed to examine the prevalence of spontaneous asthma remission or misdiagnosis among adults with recently diagnosed asthma, Aaron said.
"Once asthma is diagnosed it is thought of as a chronic condition and very often physicians treat it with daily medication," said Aaron. "We haven't really known how often it resolves or goes into remission."
He added that among study participants without evidence of asthma during the study, 14% had their initial diagnosis confirmed with airflow testing.
"These patients were correctly diagnosed and were in remission," he said. "About half of the patients (without evidence of asthma) didn't have spirometry initially, and many of these patients may have been improperly diagnosed."
The final study analysis included 613 randomly selected patients from 10 Canadian cities diagnosed with asthma within the previous five years. Those using long-term oral steroids and those who were not able to be tested with spirometry were excluded from the study.
Information from the diagnosing physician was sought to determine how the diagnosis of asthma was originally made.
All study participants were assessed with home peak flow and symptom monitoring, spirometry, and serial bronchial challenge tests, and those using daily asthma medications had their medications gradually tapered off over four study visits.
Patients with asthma ruled out by the airflow testing were followed clinically for an additional year with repeated bronchial challenge testing performed.
Mean age of the initial 701 participants was 51 and 67% were women.
Of the 613 patients who completed the study and could be conclusively evaluated for a diagnosis of current asthma:
Current asthma was ruled out in 203 of the 613 (33.1%; 95% CI 29.4%-36.8%)
Twelve of these patients (2.0%) were found to have serious cardiorespiratory conditions that had been previously misdiagnosed as asthma in the community
A total of 181 (29.5%; 95% CI 25.9%-33.1%) continued to exhibit no clinical or laboratory evidence of asthma after an additional 12 months of follow-up
Compared with those in whom asthma was confirmed, those whose asthma was ruled out were less likely to have undergone testing for airflow limitation in the community at the time of initial diagnosis (43.8% versus 55.6%, respectively; absolute difference 11.8%; 95% CI 2.1%-21.5%)
The findings mirror those of a previous study by Aaron and colleagues, which failed to confirm asthma in about one-third of patients with previously diagnosed asthma. Other cross-sectional studies from Italy and the Netherlands have also suggested that asthma is overdiagnosed in adults and children, but those cohorts were highly selected, the researchers noted.
"The current study has the advantage of having randomly recruited participants from the community," they wrote. "A further strength of the current study is that participants were studied longitudinally over 12 weeks using objective, rigorous diagnostic algorithm, which was followed by pulmonologist assessment to try to rule in or rule out current asthma."
Study limitations included the fact that a significant number of initially contacted patients declined to participate in the study, the exclusion of patients using long-term oral glucocorticoids, and the fact that fewer than half (45%) of participants were using daily asthma controller medications.
"The study design may have left out a substantial number of individuals with moderate-to-severe asthma, making it difficult to estimate the rate of remission of adult-onset asthma across the full spectrum of asthma activity, wrote Helen Hollingsworth, MD, and George T. O'Connor, MD, of Boston University School of Medicine, in an editorial published with the study.
Current asthma management guidelines recommend frequent monitoring of asthma control, and increasing medication when control is poor. They also recommend tapering patients off medications, if possible, following a period of sustained good control, Aaron noted.
"That is what we should be doing, but in reality almost none of us do that," he said. "Doctors often have the philosophy that if it's not broke don't fix it. Once a patient is feeling better we have a tendency to just leave them on the medication, but we shouldn't be doing that. We are supposed to be minimizing the burden of medication for our patients."
Agency San Francisco
San Francisco, California
Charles L. Berman
Liz Di Bernardo
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