Asthma-Associated COPD Etiotype: Clinical Features and Inflammatory Patterns in Biological Samples

Background: The Global Initiative for Chronic Obstructive Lung Disease (GOLD) recognizes asthma as a potential causal pathway for chronic obstructive pulmonary disease, referred to as the COPD-A etiotype. However, the clinical and inflammatory characteristics of this phenotype remain poorly defined. Objectives: This study aimed to characterize clinical traits and cytokine profiles in stable asthmatics exhibiting persistent airflow limitation compatible with COPD-A. Methods: In this cross-sectional study, 94 stable asthmatic patients (71.3% female; age = 54.0 ± 15.6 years) without relevant smoking or environmental exposures were evaluated. COPD-A was defined by a post-bronchodilator FEV₁/FVC ratio < 0.70. Asthma control (ACQ, ACT), quality of life (AQLQ), and lung function were assessed. Levels of IL-5, IL-8, IL-13, IL-17A, IL-17F, IL-25, IL-33, and TNF were quantified in nasal lavage, induced sputum, and blood samples. Results: Among the participants, 42 (44.7%) fulfilled COPD-A criteria. Compared with non-COPD-A subjects, those with COPD-A were older (60.5 vs. 48.7 years; p < 0.001) and had longer disease duration (39.8 vs. 30.1 years; p < 0.001), lower post-bronchodilator FEV₁% predicted (68.1 vs. 87.1%; p < 0.001), and poorer asthma control (ACQ = 1.00 vs. 0.64; p = 0.003). Cytokine levels were comparable between groups except for higher IL-8 concentrations in induced sputum of COPD-A subjects (7.66 vs. 2.51 pg/mL; p = 0.024). Sputum IL-8 ≥ 3.096 pg/mL independently predicted COPD-A (aOR = 12.82; p = 0.023). Conclusions: Over 40% of non-smoking asthmatics exhibited persistent airflow limitation consistent with COPD-A. Elevated sputum IL-8 levels may be a potential biomarker of this etiotype.