Comparison of characteristics between the original sample and the external validation sample
| Original | External validation | |||
| Total | No COPD | COPD# | ||
| Subjects n | 818 | 676 | 398 | 278 |
| Age yrs | 58.2±11.2 | 52.3±7.3 | 50.6±6.9 | 54.7±7.0 |
| Males n (%) | 403 (49.3) | 397 (58.7) | 225 (57.3) | 172 (62.3) |
| Body mass index kg·m−2 | 28.3±5.7 | 25.4±4.2 | 25.5±4.2 | 25.2±4.1 |
| Current smokers n (%) | 364 (44.5) | 676 (100) | 398 (100) | 278 (100) |
| Smoking history pack-yrs | 25.6±24.3 | 40.4±19.3 | 38.1±19.1 | 43.6±19.0 |
| FTND | NR | 4.45±1.4 | 4.39±1.4 | 4.53±1.5 |
| FEV1 post-BD % pred | 94.4±17.0 | 88.2±16.4 | 94.1±11.9 | 79.7±18.1 |
| FVC post-BD % pred | 95.8±15.5 | 101.4±15.8 | 99.9±13.7 | 103.6±18.2 |
| FEV1/FVC post-BD % pred | 98.2±9.7 | 89.5±11.9 | 97.5±6.0 | 78.1±8.3 |
Data are presented as mean±sd, unless otherwise indicated. Original sample data from 8. COPD: chronic obstructive pulmonary disease; FTND: Fagerström Test for Nicotine Dependence (range 0 (lowest level of nicotine dependence)–10 (highest)); FEV1: forced expiratory volume in one second; post-BD: post-bronchodilator; % pred: & predicted; FVC: forced vital capacity; NR: not reported. #: defined by post-BD FEV1/FVC of <0.70, according to the 2006 Global Initiative for Chronic Obstructive Lung Disease guideline 14.