Association of Mucus Plugging and Body Mass Index in Patients With Advanced COPD GOLD 3/4 With Emphysema.

Background: COPD is classified by its clinical phenotypes-chronic bronchitis and emphysema. A CT-based mucus plug score (MPS) was recently identified as a biomarker to subgroup COPD patients with increased airway mucus plugs. While not necessarily linked to more pronounced symptoms or structural lung changes, mucus plugs are associated with increased mortality. Interestingly, a higher MPS seems to be associated with a lower body mass index (BMI), likewise associated with increased mortality. This study aims to characterize patients with advanced lung emphysema presenting for lung volume reduction therapy with a special focus on mucus plug occurrence.

Material and methods: This retrospective, monocentric study assessed MPS in advanced COPD (GOLD III/IV) and emphysema patients evaluated for lung volume reduction therapy at Charité-Universitätsmedizin Berlin. CT scans were analyzed for mucus plugging, and clinical data were obtained from the Lung Emphysema Registry (www.lungenemphysemregister.de).

Results: A total of 127 CT scans were assessed for MPS. About 50% had no mucus plugs (score = 0), 25% had an intermediate burden (score 1-2), and 25% had a high burden (score ≥3). Higher MPS correlated with lower BMI, more pronounced emphysema, and worse lung function, including forced expiratory volume in 1 second, vital capacity, and diffusing capacity of carbon monoxide. Residual volume, pCO2, the 6-minute walk test, and quality-of-life parameters were unaffected. Multivariate regression analysis found a strong association between mucus plugs and BMI, showing that a decrease in BMI was associated with a higher mucus burden (p<0.001; coefficient of -1.584).

Interpretation: This study supports an association between high MPS and BMI in a vulnerable subgroup of advanced COPD patients. Further research is needed to understand the pathophysiology and consequences of mucus plugs, aiming for individualized risk assessments and treatment strategies.