Mucus plugging is associated with systemic inflammation in COPD

<bold>Background:</bold> Mucus plugging is a radiological biomarker associated with disease severity, risk of exacerbations and all-cause mortality in COPD and a potential treatable trait. The relationship between mucus plugging and biomarkers of neutrophilic and systemic inflammation has not yet been explored. We hypothesized that mucus plugging is associated with increased blood neutrophil count (BNC) and markers of systemic inflammation. Methodology We conducted a cross-sectional study of the EXCEL London COPD cohort. Presence of mucus plugs was determined on CT thorax scans using a computer assisted scoring system (VIDA Diagnostics). C-reactive protein, fibrinogen and full blood count were collected on the day of the CT scan. Patients were divided into 3 groups: no mucus plugs (A), mucus plug score 1 to 2 (B), and mucus plug score ≥ 2 (C). <bold>Results:</bold> There were 81 COPD participants included. BNC was significantly increased in patients with mucus plugs (groups B and C) 4.8x10*9/L and 4.3x10*9/L compared to those with no plugs (A) 3.6x10*9/L (P=0.024). Fibrinogen was also significantly greater in group B and C 3.6 g/L compared to those with no mucus plugs (A) 3.2 g/L (P=0.02). Multivariate analysis found no difference in BNC between groups after adjusting for age, sex, BMI, FEV1/FVC and exacerbation frequency. However, Fibrinogen remained increased in patients with mucus plugs (B and C) compared to no mucus plugs (A) following adjustment for multiple variables. Other markers of systemic inflammation were not different between groups. <bold>Conclusion:</bold> Mucus plugging was associated with increased Fibrinogen and BNC. Further mechanistic studies are needed to identify treatments to reduce mucus plugging and improve outcomes.