*2.2. Spirometry and Lung Computed Tomography (CT)*

Spirometry and bronchial reversibility test (after 400 μg of albuterol) were assessed according to the standards of the American Thoracic Society [22], using a Jaeger MasterLab spirometer (Jaeger-Toennies GmbH, Hochberg, Germany). Persistent airflow limitation was defined as an FEV1/VC index below 0.7 or FEV1 less than 0.8 of the predicted value after the bronchodilator.

Lung computed tomography (CT) was performed after 400 μg albuterol administration, using 64-raw multidetector computed tomography (Aquilion TSX-101A, Toshiba Medical Systems Corporation, Otawara, Japan) in helical scanning mode (CT parameters: 64 × 0.5 mm collimation, the helical pitch of 53 and 0.5 s per rotation with standard radiation dose (150 ± 50 mAs and 120 kVp)). The automated AW Server program (Thoracic VCAR, General Electric Healthcare, Wauwatosa, WI, USA) was applied to quantify the cross-sectional geometry of the airways at the site of the right upper lobe apical segmental bronchus (RB1) and the right lower lobe basal posterior bronchus (RB10), including the lumen and wall area, average wall thickness, wall area ratio (WAR, i.e., average difference between the outer and inner areas divided by the outer area), and wall thickness ratio (WTR, i.e., wall thickness divided by the outer diameter) [23]. Spirometry and lung CT measurements were performed only in subjects with asthma.
