Baseline characteristics of the subpopulation
| Non-smoking controls | Smoking controls | COPD | p Value | |
| No of subjects | 11 | 12 | 28 | |
| Age (years) | 63 (57–66) | 63 (59–69) | 66 (60–71) | 0.365 |
| Body mass index | 25 (23–26) | 27 (26–29) | 25 (23–30) | 0.195 |
| Sex | ||||
| Men (%) | 6 (55) | 11 (92) | 20 (71) | 0.135 |
| Women (%) | 5 (45) | 1 (8) | 8 (29) | |
| Smoking history | ||||
| Pack-years | 0 | 38 (35–46) | 43 (32–57) | <0.001 |
| Smoking status | ||||
| Current smokers (%) | 0 (0) | 6 (50) | 16 (57) | |
| FEV1 (litre) | 3 (2.51–3.83) | 3.39 (2.40–3.59) | 1.38 (0.86–2.03) | <0.001 |
| FEV1 (% predicted) | 108 (92–125) | 104 (85–113) | 48 (38–72) | <0.001 |
| FVC (litres) | 3.67 (2.96–4.84) | 4.48 (3.51–4.87) | 3.26 (2.74–3.63) | 0.005 |
| FEV1/FVC | 0.83 (0.81–1.040) | 0.73 (0.72–0.75) | 0.46 (0.39–0.56) | <0.001 |
| GOLD stages | ||||
| GOLD 1 (%) | 4 (14) | |||
| GOLD 2 (%) | 9 (32) | |||
| GOLD 3 (%) | 9 (32) | |||
| GOLD 4 (%) | 6 (22) | |||
| Emphysema | ||||
| CT evidence (%) | 1 (8) | 19 (68) | 0.001 | |
| No CT evidence (%) | 11 (92) | 9 (32) | ||
| Median elastin antibodies (relative units) | 51 (22–59) | 27 (22–43) | 44 (35–55) | 0.098 |
| Median collagen V antibodies (relative units) | 17 (1–40) | 15 (11–28) | 26 (20–38) | 0.206 |
Parameters are expressed as median (IQR). Sex, smoking status, GOLD class and the presence of emphysema are expressed as numbers and percentages (%). Kruskall–Wallis or Fisher exact p values are reported.
COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; GOLD, Global Initiative for Chronic Obstructive Lung Disease.