May 12, 2016
2 min read

Spirometry use to define COPD too narrow to include smoking-related issues

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Symptomatic current or former smokers with preserved lung function, although they do not meet the current criteria for chronic obstructive pulmonary disease, experience exacerbations, activity limitation and evidence of airway disease, according to data published in The New England Journal of Medicine.

In addition, the researchers concluded that many of these patients currently use a range of respiratory medications without any evidence base.

“Among the criteria that are needed to make a diagnosis of COPD are deficits in the rate at which one can forcefully exhale,” Prescott G. Woodruff, MD, of the University of California, San Francisco, and colleagues wrote. “However, some smokers who do not have airflow obstruction — those whose [ratio of forced expiratory volume in 1 second (FEV1) to forced vital capacity (FVC)] after bronchodilator use is equal to or greater than the conventionally accepted cutoff of 0.7 — nonetheless report cough, sputum production and shortness of breath; these symptoms are suggestive of COPD.”

To investigate smokers with normal lung function and COPD symptoms, the researchers conducted an observational study with 2,736 participants, including current or former smokers and a control group made up of patients who had never smoked. The researchers measured the participants’ respiratory symptoms using the COPD Assessment Test.

Specifically, they examined whether current or former smokers with preserved pulmonary function, as determined by spirometry, had a higher risk for respiratory exacerbations than current or former smokers with preserved lung function who were without symptoms. In addition, the researchers examined whether those with symptoms produced different results from the asymptomatic group in 6-minute walking distance, lung function or high-resolution CT chest scan.

According to the researchers, respiratory symptoms were present in 50% of the current or former smokers with preserved lung function. In addition, the mean rate of respiratory exacerbations among the symptomatic smokers was higher than the rates among those who were asymptomatic or in the control group (0.27 ± 0.67 vs. 0.08 ± 0.31 and 0.03 ± 0.21 events, respectively, per year; P < .001 for both comparisons). Current or former smokers who were symptomatic, regardless of their history of asthma, experienced greater limitation of activity, slightly lower FEV1, FVC and inspiratory capacity, and greater airway-wall thickening without emphysema compared with those without symptoms. Among current or former smokers with symptoms, 42% used bronchodilators and 23% used inhaled glucocorticoids.

“Respiratory symptoms and exacerbations are common in current or former smokers who have spirometric values that are generally considered to be within the normal range,” Woodruff and colleagues wrote. “Many of these patients are already being treated with respiratory medications despite a lack of data from clinical trials. This finding suggests that the current use of spirometry to define who should receive a diagnosis of COPD may not adequately cover the breadth of symptomatic smoking-related lung disease.” – by Jason Laday

Disclosure: Woodruff reports receiving personal fees from AstraZeneca, Genentech, Johnson & Johnson, Neostem, Novartis and Roche. He also reports a grant from the NIH. Please see the full study for a list of all other authors’ relevant financial disclosures.