Quantitative CT-derived lobar inter-tapering as a candidate imaging feature associated with airway-predominant non-emphysematous COPD.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a heterogeneous disorder involving varying contributions from airway abnormalities and emphysematous destruction. However, structural airway alterations in patients with airflow limitation but minimal emphysema remain incompletely characterized. Quantitative CT (QCT)-based airway morphology analysis may capture additional aspects of airway geometry associated with airway-predominant structural patterns. OBJECTIVES: This study aimed to evaluate lobar airway inter-tapering abnormalities on quantitative CT in patients with non-emphysematous COPD (NE-COPD) and investigate whether incorporation of inter-tapering features improves discrimination within the studied cohort. METHODS: This retrospective cross-sectional study included 173 participants who underwent inspiratory thin-section chest CT and post-bronchodilator pulmonary function testing between January 2023 and March 2025. NE-COPD was defined as airflow limitation with minimal emphysema quantified by low-attenuation area percentage below -950 HU (LAA%-950 < 5%). Automated airway segmentation and centerline-based analysis were used to quantify fourth-generation lobar inter-tapering indices. A clinical model incorporating age, sex, and smoking exposure was constructed. An imaging-augmented model was subsequently developed using LASSO-selected lobar inter-tapering features together with global airway branching complexity. Model performance was evaluated using receiver operating characteristic analysis, bootstrap validation, calibration assessment, decision curve analysis, and SHAP interpretation. RESULTS: Among the 173 participants, 87 had NE-COPD and 86 were Non-COPD controls. Compared with Non-COPD controls, patients with NE-COPD demonstrated altered fourth-generation lobar inter-tapering patterns in multiple lobes. The clinical model achieved an area under the curve (AUC) of 0.717. After incorporation of quantitative airway features, the imaging-augmented model demonstrated improved discrimination, with an AUC of 0.851. Bootstrap validation demonstrated stable model performance. SHAP analysis indicated that four lobar fourth-generation inter-tapering indices accounted for a substantial proportion of feature contribution within the fitted model. Decision curve analysis suggested higher theoretical net benefit of the imaging-augmented model within the evaluated threshold probability range. CONCLUSION: Quantitative CT-derived lobar inter-tapering was associated with pulmonary function-defined non-emphysematous COPD. These findings suggest that lobar inter-tapering represents a candidate geometric CT descriptor for characterizing airway-predominant structural patterns. Further multicenter studies with external validation and integration of complementary quantitative CT descriptors are required to determine its broader clinical utility.