Severe Asthma Phenotypes Classified by Site of Airway Involvement and Remodeling via Chest CT Scan
Kim S1, Nam Jin K4, Cho SH2,3, Hyun Lee C5*, Kang HR2,3*
1Department of Internal Medicine, School of Medicine, Kyungpook National University, Daegu, Korea
2Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul National University College of Medicine, Seoul, Korea
3Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea
4Department of Radiology, SMG-SNU Boramae Medical Center, Seoul, Korea
5Department of Radiology, Seoul National University College of Medicine, Seoul, Korea
J Investig Allergol Clin Immunol 2018; Vol. 28(5)
Objectives: This study aimed to establish a system that can classify severe asthma on the basis of airway remodeling patterns visualized by computed tomography (CT) images and to evaluate the clinical characteristics of individual image-based subtypes.
Methods: Chest CT images of 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), or bronchiectasis (BE). BT severity and MP extent score were independently associated with peripheral blood eosinophil count (P = 0.012, r2 = 0.112) and sputum eosinophil count (P = 0.022, r2 = 0.090), respectively. The large-to-medium airway remodeling type (LA type), showing diffuse BT combined with MP and BE, accounted for 44% of the total patients and revealed higher peripheral blood eosinophil counts than other types. The small airway remodeling type (SA type), which accounted for 6.6%, showed a higher rate of fixed airflow obstruction, along with male- and smoker-predominance and more controller medication use than other phenotypes. In 26% of patients with severe asthma, no prominent airway remodeling was observed (near-normal type, NN type); NN type showed less requirement for oral steroid relative to LA and SA types.
Conclusions: Three different structural types can be distinguished by chest CT findings, depending on the site of airway involvement and remodeling pattern in lungs of patients with severe asthma. Remodeling in large-to-medium sized airways revealed an association with systemic eosinophilic inflammation in severe asthma.
Key words: Asthma, Phenotype, Tomography, X-ray, Airway remodeling