Table 1– Continuous variables (anthropometric data, smoking, pulmonary function and computed tomography (CT) measurements) of 473 chronic obstructive pulmonary disease patients

	Learning set	Testing set	p-value
Subjects n	100	373
Age years	63±10	68±8	<0.01
BMI	25.6±4	26.3±5	ns
Smoking pack-years	50.4±36	48.5±30	ns
FVC % pred	84.6±24	85.4±19	ns
FEV₁ % pred	55.9±24	60.9±20	<0.05
FEV₁/VC	45.6±14	50.7±13	<0.01
FEV₁/FVC	53.1±13	56±12	<0.05
TLC % pred	109.8±17	106±16	<0.05
RV % pred	148.1±53	138.7±40	<0.05
RV/TLC	51.2±11	50.7±10	ns
FRC % pred	131.7±34	123±30	<0.05
VC % pred	92.2±21	91±18	ns
IC % pred	90.8±26	92.8±22	ns
D_LCO % pred	69.2±23	72.3±23	ns
%LAA_-950^#	15.7±13
AWT-Pi10^#	3.9±0.1

Data are presented as mean±sd, unless otherwise stated. BMI: body mass index; pack-years: number of packs of cigarettes per day multiplied by the number of smoking years; FVC: forced vital capacity; % pred: % predicted; FEV₁: forced expiratory volume in 1 s; VC: vital capacity; TLC: total lung capacity; RV: residual volume; FRC: functional residual capacity; IC: inspiratory capacity; D_LCO: single breath diffusion capacity of the lung for carbon monoxide; %LAA_-950: relative attenuation area with X-ray attenuation < -950 HU; AWT-Pi10: average wall thickness of an arbitrary airway with an internal perimeter of 10 mm; ns: not significant. ^#: reported only for the 100 patients of the learning set who underwent CT scanning.