Investigation of Clinical Characteristics and Functional Abnormalities of Asthma-COPD Overlap in Patients with Severe Asthma: A Comprehensive Tertiary Care Analysis

Background: Asthma–COPD overlap (ACO) is an increasingly recognized but underdiagnosed phenotype associated with greater disease severity, accelerated lung function decline, and complex therapeutic requirements compared with asthma or COPD alone. Objective: To determine the prevalence of ACO among patients with severe asthma, describe demographic and clinical characteristics, evaluate pulmonary function and inflammatory biomarkers, and support improved recognition and individualized management. Methods: A prospective cross-sectional study included 122 consecutive patients with severe asthma evaluated at a tertiary respiratory center. ACO was defined using GINA/GOLD syndromic criteria requiring ≥3 features of both asthma and COPD. Assessments included spirometry, HRCT with emphysema quantification, DLCO, FeNO, blood and sputum eosinophils, total IgE, medication history, and symptom severity. Results: Thirty-five patients (28.7%) fulfilled criteria for ACO. These patients were older, predominantly male, had longer disease duration, and showed markedly higher smoking exposure (91.4% with ≥10 pack-years). ACO patients demonstrated fixed airflow obstruction, lower FEV₁, and significantly higher emphysema burden on HRCT. A mixed inflammatory pattern was observed, characterized by elevated IgE with relatively suppressed eosinophilic markers and FeNO. Chronic oral corticosteroid use was more frequent in ACO than in pure asthma. Conclusion: ACO is common among severe asthma patients and represents a distinct clinical phenotype requiring early identification and tailored management integrating asthma and COPD treatment principles.