Differences in airway structural changes assessed by 3-dimensional computed tomography in asthma and asthma-chronic obstructive pulmonary disease overlap.

BACKGROUND: Asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) is a clinical phenotype sharing features of asthma and COPD. Multidetector row computed tomography (MDCT) can be used to evaluate the airway structure; however, differences between asthma and ACO seen on MDCT are poorly understood. OBJECTIVE: To investigate the difference in airway structural between asthma and ACO, using MDCT in patients with clinical asthma. METHODS: Sixty-four patients with asthma were allocated to an asthma group (never smokers and ex-smokers with a smoking history of < 10 pack-years) or an ACO group (patients with a ≥10-pack-year smoking history and forced expiratory volume in 1 second [FEV1]/forced vital capacity [FVC] < 0.7). The asthma group was further divided into patients with airflow limitation (AL; FEV1/FVC < 0.7) and those without AL. Wall thickness (WT) and airway inner luminal area in the third-generation to fifth-generation bronchi were evaluated using MDCT in both study groups and in 29 healthy controls. RESULTS: Forty-three patients were included in the asthma group (20 with AL, 23 without AL) and 16 in the ACO group. Patients with asthma and ACO had significantly greater WT than the healthy controls. WT in the third-generation bronchi was significantly greater in the ACO group than in the asthma group. The ACO group and the asthma with AL group were matched for age, disease duration, and FEV1/FVC. The WT in the third-generation bronchi was still greater in the ACO group than in the asthma with AL group. CONCLUSION: Patients with ACO have a thicker airway wall than those with asthma, suggesting that airway remodeling is more prominent in ACO than in asthma. UMIN Clinical Trials Registry (UMIN-CTR) system (http://www.umin.ac.jp/ctr/UMIN000028913).