Mettler, Sofia K.

Abstract Introduction / Rationale Mucus plugs (MPs) on chest computed tomography (CT) are associated with increased respiratory symptoms, worse lung function, and elevated mortality and acute exacerbations among individuals with GOLD2-4 COPD. Whether mucus plug distribution in the upper versus lower lobes differentially impacts future acute exacerbations (AEs) has been incompletely explored. Methods Data from current and former tobacco users, ages 40-80, with ≥10 pack-years, at the enrollment visit in COPDGene were analyzed. MPs were visually-assessed on chest CTs using a sequential reading system; the MP score was calculated as the number of bronchopulmonary segments with plugs (range 0-18). Among subjects with MPs, the percent of lower lobe MPs (%LLMPs) was calculated as the number of bronchopulmonary segments in the right and left lower lobes divided by the total number of bronchopulmonary segments (range 0-100%). Moderate-to-severe AEs were assessed prospectively biannually for up to 15.5 years. Zero-inflated Poisson regression, adjusting for age, sex, BMI, race, smoking status, pack-years, FEV1% predicted, history of AEs (year prior to enrollment), and clinical center assessed the relationship between %LLMPs, total MPs, and prospective AEs; duration of follow-up was included as the offset. Subgroup analyses by lung function category (GOLD0, GOLD 1-4 COPD, and Preserved Ratio Impaired Spirometry, PRISm) were also performed using the same model. Results Among 10,198 tobacco-exposed individuals, 9,406 subjects (mean age 59.7±9.0, 53.4% male, 68% non-Hispanic white) had chest CT scans scored for MPs. The overall prevalence of MP>0 was 30.4%, with an average MP score of 0.78±1.88 and average %LLMP of 48%±39%. The prevalence of MPs varied by lung function category (20.1% GOLD0, 26.2% PRISm, 40.8% COPD) as did the mean MP score (0.28±0.93 GOLD0, 0.49±1.38 PRISm, 1.30±2.42 COPD) (Figure 1). The %LLMP also varied by lung function category (33%±39% GOLD0, 38%±37% PRISm, 57%±37% COPD). Among subjects with MPs>0 (n=2,857), higher %LLMP was associated with a significantly increased risk for future AEs (adjusted rate ratio (aRR) [95%CI]= 1.11[1.05-1.17]; Figure 1). Subgroup analyses by lung function category supported a significant association between increased %LLMP and future AEs in GOLD0 (aRR 1.45 [1.25-1.69]), but not in the COPD or PRISm subgroups (Figure 1). Conclusions A higher proportion of lower lobe mucus plugs is significantly associated with increased risk for future AEs among tobacco-exposed persons. Despite having the lowest burden of MPs, the highest risk for prospective AEs with increasing %LLMP was observed in the subgroup with normal spirometry (GOLD0).