Beathing Tests Deemed Vital for Accurate Asthma Diagnosis

A new study underscores the need of a spirometry test to properly diagnose asthma and to distinguish it from other lung diseases, such as chronic obstructive pulmonary disease (COPD).

Researchers at the University of Ottawa (Ontario, Canada), the University of British Columbia (Vancouver, Canada), and other institutions comprising the Canadian Respiratory Clinical Research Consortium (CRCRC) conducted a longitudinal study involving non-obese (i.e., people with a body mass index (BMI) of 20–25) and obese (BMI of over 30) individuals suffering from asthma that had been diagnosed by a physician. The participants were recruited from eight Canadian cities by means of random-digit dialing. A diagnosis of current asthma was excluded in those who did not have evidence of acute worsening of asthma symptoms, reversible airflow obstruction, or bronchial hyper-responsiveness, despite being weaned off asthma medications. The researchers then stopped asthma medications in those in whom a diagnosis of asthma was excluded, and then assessed their clinical outcomes over six months.

The results showed that of the 540 individuals with physician-diagnosed asthma who participated in the study, asthma was ultimately excluded in 31.8% of the participants in the obese group and in 28.7% in the non-obese group. The researchers also found that diagnosis of asthma was no more likely to occur among the obese individuals than among the non-obese individuals. Of those in whom asthma was excluded, 65.5% did not need to take asthma medication or seek health care services due to asthma symptoms during the 6-month follow-up period. The study was published in the November 18, 2008, edition of the Canadian Medical Association Journal (CMAJ).

"Our study showed that a substantial proportion of people, whether obese or not, may be overdiagnosed with asthma and may be prescribed asthma medications unnecessarily,” concluded lead author Shawn Aaron, M.D., of the University of Ottawa, and colleagues. "Physicians should consider objective testing using spirometry and, if necessary, bronchial challenge testing to confirm asthma in patients with respiratory symptoms.”

Spirometry is the most common of the pulmonary function tests (PFTs) measuring lung function, specifically the measurement of the amount (volume) and flow of air that can be inhaled and exhaled. Spirometry is an important tool used for generating pneumotachographs, which are helpful in assessing conditions such as asthma, pulmonary fibrosis, cystic fibrosis (CF), and COPD.

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University of Ottawa
University of British Columbia