Measures of reversibility are of limited value for distinguishing smoke-related chronic obstructive pulmonary disease (COPD) from asthma, but bronchodilator response (BDR) testing may be a phenotypic marker for asthma, according to study results published in European Respiratory Journal.
Researchers examined findings from 3 large population studies to compare different methods for measuring BDR in COPD and asthma and to study the extent to which BDR is related to symptom burden and phenotype traits. The investigation included 35,628 patients aged 16 years and older. Patients were categorized in 3 groups: COPD (n=1146), current asthma (n=2833), and no airway disease (n=31,649).
Lung function data were obtained from all patients using spirometry and bronchodilator reversibility. Forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) were measured before and 15 minutes after administration of 200 μg of salbutamol. In patients with COPD and current asthma, the researchers assessed the association between measures of reversibility and numerous variables including wheeze, nocturnal chest tightness, nocturnal cough attacks within the past 12 months, chronic bronchitis, number of asthma attacks in the past 3 months, and nasal allergy.
Results revealed that both flow- and volume-related bronchodilator reversibility was at least as common in smoking-related COPD as in asthma. The prevalence of BDR was significantly higher in the COPD and asthma group (FEV1≥12% and 200 mL was 18.4% and 17.3%, respectively) compared with the group without airway disease (5.1%). Additionally, the prevalence of bronchodilator reversibility was higher in COPD than in asthma for most of the definitions used in the analyses.
In asthma, bronchodilator reversibility was independently associated with wheeze (odds ratio [OR], 1.36; 95% CI, 1.04-1.79), atopic sensitization (OR, 1.36; 95% CI, 1.04-1.79) and higher measurement of fractional exhaled nitric oxide. In COPD, neither flow nor volume-related bronchodilator reversibility was linked to more symptoms or reduced health status after adjusting for prebronchodilator FEV1.
This study had a few limitations. First, the definition of asthma was based on patient-reported diagnosis, attacks, and medication. The definition of COPD excluded patients with a history of asthma and nonsmoking-related COPD. Second, the dose of salbutamol used was lower than generally recommended in some guidelines. Third, some of the variables studied were only available in a small subset of individuals with COPD.
The study researchers concluded that measures of reversibility are of limited value for distinguishing COPD from asthma. However, in asthma, measuring BDR may be a valuable phenotypic marker.
Janson C, Malinovschi A, Amaral AFS, et al. Bronchodilator reversibility in asthma and COPD: findings from three large population studies [published online June 20, 2019]. Eur Respir J. doi:10.1183/13993003.00561-2019