Computed tomography characteristics of chronic bronchitis and its association with disease severity and clinical outcomes in viral pneumonia: a retrospective cohort study.

BACKGROUND: Chronic bronchitis (CB) patients' excessive mucus and airway changes may worsen viral pneumonia severity, but there is a lack of objective clinical/imaging assessment criteria. This study used quantitative computed tomography (CT) to link CB pathology with pneumonia severity/prognosis, guiding early interventions for high-risk groups.

METHODS: This retrospective cohort study included 42 patients with CB diagnosed with viral pneumonia and 208 non-CB viral pneumonia controls. Baseline demographic, clinical, and laboratory parameters were collected alongside thoracic CT-derived metrics, including mucus plugging score (a bronchopulmonary segment-based scoring system quantifying mucus obstruction severity), CT severity score (range, 0-25 per lobe), and emphysema quantification. Follow-up CT imaging was performed at 3 months post-diagnosis to assess pulmonary structural remodeling, with longitudinal documentation of CT severity scores. Participants were stratified into two cohorts by mucus plugging score: high mucus burden (≥4, group 1) and low mucus burden (<4, group 2). Intergroup comparisons utilized Fisher's exact test for categorical variables, with continuous variables analyzed via independent t-tests (normally distributed) or Mann-Whitney U tests (non-parametric distributions). Multivariate logistic regression modeling identified independent predictors of disease progression.

RESULTS: This study enrolled 260 patients who were categorized into group 1 (n=42; CB prevalence: 35.70%) and group 2 (n=218; CB prevalence:19.70%). Comparative analysis demonstrated that CB patients in group 2 were significantly older [70, interquartile range (IQR) (62, 77) vs. 79, IQR (74.5, 86.5) years; P<0.001] and exhibited a higher female predominance (74.4% vs. 25.6%; P=0.03), alongside lower red blood cell count (RBC) [3.73, IQR (3.39, 4.29)×1012/L vs. 4.05, IQR (3.81, 4.53)×1012/L; P=0.02] and hemoglobin levels [119, IQR (105.5, 131) vs. 124, IQR (115.5, 136) g/L; P=0.04] compared to non-CB counterparts. Imaging analysis revealed that non-CB patients had greater thoracic reticular patterns [6.02, IQR (1.42, 10.08) vs. 2.50, IQR (0.57, 6.19) cm3; P=0.02] and emphysema severity [0.21, IQR (0.04, 0.73) vs. 0.05, IQR (0.01, 0.19) cm3; P<0.001], whereas CB patients across both groups showed marked bronchial wall thickening [group 1: 21.60, IQR (10.30, 37.69) vs. 6.28, IQR (1.54, 15.71) cm3, P=0.03; group 2: 35.08, IQR (13.38, 51.59) vs. 18.90, IQR (3.43, 45.53) cm3, P=0.01]. Notably, CB patients in group 2 displayed larger bronchial lumen volumes [13.63, IQR (5.19, 25.29) vs. 5.00, IQR (0.67, 13.46) cm3; P<0.001]. Multivariate analysis of the low mucus burden group identified female sex [odds ratio (OR) =3.39], age (OR =1.06), and emphysema (OR =1.56) as independent risk factors for disease progression (all P<0.05). Longitudinal CT follow-up indicated stable severity scores in non-CB patients, whereas high mucus-secreting CB patients (group 1) demonstrated significant reductions in mucus plugging scores over time.

CONCLUSIONS: CB features-mucus hypersecretion, emphysema, and airway thickening-worsen viral pneumonia severity and prognosis. Key predictors include advanced age (OR =1.06), female sex (OR =3.39), and emphysema (OR =1.56). High-risk CB patients, especially with emphysema, need enhanced CT monitoring and therapies improving mucociliary clearance and airway repair.