Mucus plugging on CT and mortality in smokers

Background: Mucus dysfunction, a key pathophysiologic feature of chronic obstructive pulmonary disease (COPD), is characterized by increased mucus production and plug formation in the airways leading to airflow obstruction. Computed tomography (CT) has been recently used to identify mucus plugs, providing an alternative way to assess mucus dysfunction. We aimed to test whether mucus plugging on CT is associated with mortality in smokers. Methods: We identified and scored mucus plugging in the intra-parenchymal airways on CT scans from 500 smokers with and without COPD from the COPDGene Study. We used a score based on the number of bronchopulmonary segments with mucus plugs. The score ranges from 0 to 18, with higher values indicating greater burden of mucus plugging on CT. We used Cox regression multivariable models to test the association between mortality and mucus plugging. Results: Ninety-eight subjects (20%) had mucus plugging on CT, with a median score of 2 (range, 1-13). During a follow-up of 7.5 years, 140 (28%) subjects died. After adjusting for age, gender, race, body mass index, current smoking status, pack-years, CT measures of emphysema, and COPD status, a higher mucus plugging score was associated with increased risk of all-cause mortality (per 1-point increase, Hazard Ratio 1.18, 95% Confidence Interval 1.07-1.30) (Figure 1). Conclusion: CT-identified mucus plugging has a prognostic value in smokers. Mucus plugging might be a distinct imaging phenotype.