| Stage I | Stage II | Stage III | |
| Subjects n | 223 | 486 | 121 |
| FVC | |||
| % pred | 102.7 (73.9–127.5) | 98.0 (72.7–122.2) | 90.2 (56.2–112.4) |
| SR | 0.22 (-1.88–2.30) | -0.15 (-2.25–1.71) | -0.78 (-3.42–0.98) |
| Subjects with low FVC % | 4.0 | 8.2 | 19.8 |
| FEV1 | |||
| % pred | 100.8 (71.4–128.3) | 95.4 (64.3–120.9) | 88.2 (50.8–113.9) |
| SR | 0.07 (-2.21–2.46) | -0.38 (-2.89–1.78) | -1.0 (-4.11–1.09) |
| Subjects with low FEV1 % | 8.1 | 15.8 | 25.6 |
| FEV1/FVC | |||
| % | 80.5 (70.3–91.0) | 79.6 (63.8–92.7) | 79.5 (64.7–94.1) |
| SR | -0.32 (-2.34–1.26) | -0.44 (-2.95–1.55) | -0.37 (-2.82–1.97) |
| Subjects with obstruction % | 6.3 | 13.2 | 15.7 |
| FEF25–75% | |||
| % pred | 87.9 (40.8–137.6) | 81.8 (32.5–138.9) | 74.0 (27.5–137.3) |
| SR | -0.50 (-2.48–1.78) | -0.72 (-2.64–1.79) | -1.02 (-2.99–1.69) |
| Subjects with reduced FEF25–75% % | 13.5 | 23.0 | 28.9 |
| TLC | |||
| % pred | 107.2 (82.4–134.2) | 103.7 (77.7–129.7) | 97.1 (62.3–121.3) |
| SR | 0.62 (-1.7–2.97) | 0.31 (-2.14–2.57) | -0.30 (-3.01–1.77) |
| Subjects with low TLC % | 2.7 | 5.3 | 21.5 |
| VC | |||
| % pred | 111.8 (84.1–144.5) | 107.0 (78.5–138.7) | 100.0 (60.6–128.2) |
| SR | 0.92 (-1.50–3.30) | 0.52 (-2.12–2.81) | -0.08 (-2.81–1.94) |
| Subjects with low VC % | 1.8 | 3.9 | 15.7 |
| RV/TLC | |||
| % pred | 92.0 (57.3–124.0) | 95.9 (64.3–130.8) | 98.4 (63.9–142.0) |
| SR | -0.40 (-2.13–1.37) | -0.21 (-2.00–1.66) | -0.1 (-2.19–2.19) |
| Subjects with high RV/TLC % | 1.3 | 2.9 | 5.8 |
| DL,CO | |||
| % pred | 92.4 (69.9–118.4) | 87.1 (59.4–113.5) | 77.9 (42.4–105.7) |
| SR | -0.60 (-2.42–1.41) | -0.97 (-3.13–1.12) | -1.63 (-4.03–0.51) |
| Subjects with low DL,CO % | 13.0 | 26.7 | 44.6 |
| CL,s | |||
| % pred | 77.6 (42.7–127.6) | 69.6 (34.8–110.0) | 62.4 (17.6–112.4) |
| SR | -0.88 (-2.35–0.97) | -1.19 (-2.69–0.35) | -1.50 (-3.23–0.45) |
| Subjects with low CL,s % | 17.0 | 29.2 | 42.1 |
| CL,s reference values# | |||
| % pred | 86.1 (53.0–126.9) | 77.9 (41.5–116.9) | 70.5 (24.9–119.6) |
| SR | -0.73 (-2.79–1.47) | -1.15 (-3.25–0.88) | -1.55 (-3.79–1.07) |
| Subjects with low CL,s % | 21.5 | 33.5 | 46.3 |
Values are expressed as mean (95% CI), unless otherwise stated. FVC: forced vital capacity; % pred: % predicted; SR: standardised residual; FEV1: forced expiratory volume in 1 s; FEF25–75%: forced expiratory flow at 25–75% FVC; TLC: total lung capacity; VC: vital capacity; RV: residual volume; DL,CO: diffusing capacity of the lung for carbon monoxide; CL,s: static lung compliance. #: reference values from Begin et al. 25.