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Severe Asthma Phenotypes Classified by Site of Airway Involvement and Remodeling via Chest CT Scan

Kim S1, Lee CH2*, Jin KN3, Cho SH4,5, Kang HR4,5*

Department of Internal Medicine, School of Medicine, Kyungpook National University, Kyungpook National University Hospital, Daegu, Korea
2Department of Radiology, Seoul National University College of Medicine, Seoul, Korea
3Department of Radiology, SMG-SNU Boramae Medical Center, Seoul, Korea
4Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul National University College of Medicine,Seoul, Korea
5Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea
*These authors contributed equally to this article.

J Investig Allergol Clin Immunol 2018; Vol 28(5) : 312-320
doi: 10.18176/jiaci.0265

Objectives: This study aimed to establish a system that can classify severe asthma on the basis of airway remodeling patterns visualized using computed tomography (CT) images and to evaluate the clinical characteristics of individual image-based subtypes.
Methods: Chest CT images from severe asthma patients were retrospectively evaluated to classify phenotypes by site of airway involvement and remodeling. The association between radiologic subtypes and clinical characteristics was assessed.
Results: Of 91 patients with severe asthma, 74 (81.3%) exhibited abnormal radiologic findings, including bronchial wall thickening (BT), mucus plugging (MP), and bronchiectasis (BE). The severity of BT and the extent of MP were independently associated with peripheral blood eosinophil count (P=.012, r2=0.112) and sputum eosinophil count (P=.022, r2=0.090), respectively. The large-to-medium airway remodeling type, which showed diffuse BT combined with MP and BE, accounted for 44% of patients and revealed higher peripheral blood eosinophil counts than other types. In the small airway remodeling type, which accounted for 6.6% of patients, we observed a higher rate of fixed airflow obstruction, along with a predominance of males and smokers and more frequent use of controller medication than other phenotypes. In 26% of patients with severe asthma, no prominent airway remodeling was observed (near-normal type); the near-normal type required oral corticosteroids less frequently than the large-to-medium airway and small airway remodeling types.
Conclusions: Depending on the site of airway involvement and remodeling pattern, 3 different structural types can be distinguished in chest CT findings from patients with severe asthma. Remodeling in large-to-medium sized airways revealed an association with systemic eosinophilic inflammation in patients with severe asthma.

Key words: Asthma, Phenotype, Tomography, X-ray, Airway remodeling