| COPD subjects(n = 195) | Smoker controls(n = 36) | Non-smoker controls(n = 36) | p Value† | |
| Age | 64.5 (6.0) | 60.8 (7.7) | 59.7 (8.8) | 0.002 |
| Male (%) | 141 (72) | 24 (67) | 14 (39) | 0.492 |
| Smoking history (pack-years) | 45.8 (27.2) | 29.8 (16.5) | 1 (0) | <0.001 |
| FEV1 (l) | 1.2 (0.5) | 3.2 (0.6) | 3.1 (0.7) | <0.001 |
| FEV1 (% pred) | 43.9 (16.9) | 108.9 (11.8) | 115.8 (12.0) | <0.001 |
| FEV1/FVC | 0.40 (0.12) | 0.80 (0.06) | 0.80 (0.05) | <0.001 |
| CT scans (n)* | 178 | 29 | 32 | |
| % Low attenuation area (<−950 HU) | 22.6 (13.5) | 4.5 (4.4) | 5.4 (5.5) | <0.001 |
| Baseline CC-16 (ng/ml), median (IQR) | 5.9 (3.9) | 6.3 (2.3) | 7.5 (4.3) | 0.117 |
| Number of CC-16 results at 3 months | 182 | 35 | 34 | |
| 3 month CC-16 (ng/ml), median (IQR) | 5.7 (3.6) | 6.6 (3.3) | 8.2 (4.3) | 0.046 |
All values are number or mean and standard deviation (in brackets) unless otherwise stated.
The lung function measurements were performed following the administration of 180 μg salbutamol. All the smoking controls and individuals with COPD were former smokers.
*CT scans is the number of CT scans available for qualitative analysis to assess the percentage of the lungs with a density of less than −950 HU.
†p values for difference between COPD subjects and smoker controls. All the parameters measured were significantly different between individuals with COPD and non-smoker controls (p⩽0.005).
CC-16, Clara cell secretory protein-16; COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; IQR, interquartile range.