Table 2– Demographic and physiological data from 41 cases of smokers with idiopathic interstitial pneumonia from phase 1 (derivation group)

	Former smokers	Current smokers	p-value
Subjects	14	27
Age years	55.1±8.7	52.7±11.2	0.49
Males/females	11/3	20/7	0.23
Smoking history pack-years	34.5±24.59	38.4±19.3	0.59
Clinical history
Cough yes/no	13/1	24/2	0.96
Duration of cough months	18.5±18.3	12.4±16.7	0.30
Dyspnoea yes/no	14/0	26/1	0.75
Duration of dyspnoea months	18.9±17.0	13.1±17.2	0.31
Pulmonary function
FVC % predicted	71.7±22.6	77.0±19.3	0.44
FEV₁ % predicted	76.4±18.2	75.5±18.8	0.89
FEV₁/FVC	81.3±8.9	77.1±12.5	0.28
D_LCO % predicted	46.1±18.1	57.0±12.5	0.03

Data are presented as n or mean±sd, unless otherwise stated. Continuous variables were compared with t-test and categorical variables with Chi-squared test. FVC: forced vital capacity; FEV₁: forced expiratory volume in 1 s; D_LCO: diffusing capacity of the lung for carbon monoxide.