Clinical characteristics and changes of clinical features in patients with Asthma-COPD overlap in Korea according to different diagnostic criteria

Background: Asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) is a condition characterized by the overlapping clinical features of asthma and COPD. To evaluate the appropriateness of different sets of ACO definition, we compared the clinical characteristics of the previously defined diagnostic criteria and the specialist opinion in this study. Methods: Patients enrolled in the KOrea COpd Subgroup Study (KOCOSS) were evaluated. Based on the questionnaire data, the patients were categorized into the ACO and non-ACO COPD groups according to the four sets of the diagnostic criteria. Results: In total 1,475 patients evaluated: 202 of 1,475 (13.6%), 32 of 1,475 (2.2%), 178 of 1,113 (16.0%), and 305 of 1,250 (24.4%) were categorized as ACO according to the modified Spanish Society of Pneumonology and Thoracic Surgery (SEPAR), American Thoracic Society (ATS) Roundtable, Global Initiative for Asthma (GINA)/Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria, and the specialists diagnosis, respectively. The ACO group defined according to the GINA/GOLD criteria showed significantly higher St. George's Respiratory Questionnaire and COPD Assessment Test scores than the non-ACO COPD group. When the modified SEPAR definition was applied, the ACO group showed a significantly larger decrease in the forced expiratory volume in 1 second (FEV₁, %). The ACO group defined by the ATS Roundtable showed significantly larger decrease in the forced vital capacity values compared to the non-ACO COPD group (-18.9% vs. -2.2%, p=0.007 and -412 mL vs. -17 mL, p=0.036). The ACO group diagnosed by the specialists showed a significantly larger decrease in the FEV₁ (%) compared to the non-ACO group (-5.4% vs. -0.2%, p=0.003). Conclusion: In this study, the prevalence and clinical characteristics of ACO varied depending on the diagnostic criteria applied. With the criteria which are relatively easy to use, defining ACO by the specialists diagnosis may be more practical in clinical applications.