Mucus plugging, disease severity and sputum myeloperoxidase concentration in bronchiectasis

Background: Bronchiectasis is characterised by impaired mucociliary clearance, leading to persistent mucus accumulation, known as mucus plugging (MP). Myeloperoxidase (MPO) is a key molecule that activates neutrophilic inflammation during bronchiectasis, leading to disease progression. However, whether sputum MPO concentration is an independent factor associated with MP remains unclear. Methods: We retrospectively evaluated 78 patients with bronchiectasis at Chungbuk National University Hospital (Cheongju, Republic of Korea) between June 2022 and April 2023. According to the extent of MP on chest computed tomography, participants were divided into high MP (MP in >9 bronchopulmonary segments) and low MP (MP in ≤9 bronchopulmonary segments) groups. We evaluated whether sputum MPO concentration is independently associated with MP using multivariable adjusted logistic regression analyses. Results: There were 59 (75.6%) and 19 (24.4%) participants in the low and high MP groups, respectively. Compared with the low MP group, the high MP group had significantly higher disease severity, as measured by the modified Reiff score (p<0.001) and FACED score (p=0.003). Sputum MPO concentration was significantly correlated with the extent of MP (ρ=0.313, p=0.009). In addition, sputum MPO concentration was independently associated with a high extent of MP even after adjusting for potential confounders (adjusted OR 1.60 (95% CI 1.06-2.42)). Conclusions: Sputum MPO concentration was associated with a high degree of MP, suggesting a potential role of MPO in the pathogenesis of mucus plugging.