Characterization of mucus plugging in patients with chronic obstructive pulmonary disease: additional clinical significance of asthma-like features

Asthma-like features, defined as a high blood eosinophil count (BEC), atopy, and bronchodilator reversibility, characterize patients with chronic obstructive pulmonary disease (COPD) under optimal treatment. However, whether these features contribute to the phenotype of mucus plugging has not been elucidated. In this study, we aimed to examine the functional and clinical outcomes related to mucus plugging in patients with and without asthma-like features. Mucus plug score was assessed using inspiratory computed tomography (CT) scans in participants from the Hokkaido COPD cohort study who underwent CT examinations using the same protocol, were categorized based on asthma-like features, and completed the St. George’s Respiratory Questionnaire (SGRQ). To evaluate the association between mucus plug score and pulmonary function indices, multivariate analyses were performed to examine the relationships between the mucus plug score and percent predicted forced expiratory volume in 1 s (%FEV 1 ) or residual volume (RV)/total lung capacity (TLC). These analyses were adjusted for BEC or CT-derived airway indices (total airway wall volume, functional small airway disease, and emphysema index) based on asthma-like feature categorization, in addition to univariate analyses. The mucus plug score was negatively associated with %FEV 1 and FEV 1 /forced vital capacity in patients with ( N = 45) and without ( N = 46) asthma-like features and was positively associated with RV/TLC in those without asthma-like features. As the mucus plug score increased, the SGRQ score worsened in both groups. Multivariate analysis revealed a correlation between mucus plug score and RV/TLC (estimate [95% confidence interval], 1.27 [0.30, 2.25]), but not %FEV 1, in patients without asthma-like features, and between mucus plug score and %FEV 1 (− 1.26 [− 2.33, − 0.20]), but not RV/TLC, in patients with asthma-like features, after adjusting for proximal airway, small airway, and emphysema indices. Asthma-like features may differentiate the functional role of mucus plugging observed on CT scans in patients with COPD. Further studies are needed to validate these findings and clarify the underlying pathophysiology for improved disease management.