Prevalence and characteristics of asthma–COPD overlap syndrome identified by a stepwise approach

Hiromasa Inoue,1 Takahide Nagase,2 Satoshi Morita,3 Atsushi Yoshida,4 Tatsunori Jinnai,4 Masakazu Ichinose5
1Department of Pulmonary Medicine, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, 2Department of Respiratory Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, 3Department of Biomedical Statistics and Bioinformatics, Kyoto University Graduate School of Medicine, Kyoto, 4Medical Department, AstraZeneca K.K., Osaka, 5Department of Respiratory Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan

Background and objective: There is increasing recognition of asthma–COPD overlap syndrome (ACOS), which shares some features of both asthma and COPD; however, the prevalence and characteristics of ACOS are not well understood. The aim of this study was to investigate the prevalence of ACOS among patients with COPD and its characteristics using a stepwise approach as stated in the recent report of the Global Initiative for Asthma (GINA) and the Global Initiative for Chronic Obstructive Lung Disease (GOLD).
Methods: This multicenter, cross-sectional, observational study enrolled outpatients who were receiving medical treatment for COPD. Clinical data, including spirometry results, were retrieved from medical records. For symptom assessment, patients were asked to complete the Clinical COPD questionnaire and the modified British Medical Research Council questionnaire.
Results: Of the 1,008 patients analyzed, 167 (16.6%) had syndromic features of ACOS. Of the total number of patients, 93 and 42 (9.2% and 4.2%) also had a predefined clinical variability of ≥12%/≥200 mL and ≥12%/≥400 mL in forced expiratory volume in 1 second (FEV1), respectively, and therefore were identified as having ACOS. Conversely, the number of patients who had either syndromic or spirometric feature of ACOS was 595 (59.0%, ≥12%/≥200 mL FEV1 clinical variability), and 328 patients (32.5%, ≥12%/≥400 mL FEV1 clinical variability) had both the features. Patients identified as having ACOS were of significantly younger age, had a shorter duration of COPD, lower number of pack-years, better lung function, milder dyspnea symptoms, and higher peripheral blood eosinophil values compared with patients with COPD alone. The rate of exacerbations in the previous year was not significantly different between the ACOS and COPD groups.
Conclusion:
 Using a stepwise approach, as stated in the GINA/GOLD report, the proportions of patients identified as having ACOS were found to be 9.2% and 4.2% (depending on the FEV1variability cutoff used) among the 1,008 outpatients medically treated for COPD in a real-life clinical setting.

Keywords: obstructive lung diseases, airway hyperresponsiveness, respiratory function tests, differential diagnosis

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