Characteristics of groups used to train the reference equations
| Male | Female | |
| Subjects | 4846 | 6736 |
| Age# years | 42±11.6 | 42±12.4 |
| Height cm | 183±6.7 | 170±6.4 |
| Weight kg | 84±9.8 | 69±8.9 |
| BMI kg·m−2 | 24.9±2.5 | 23.9±2.8 |
| FEV1 L | 4.40±0.63 | 3.19±0.49 |
| FEV1 % pred | 99±9.1 | 98±9.2 |
| FVC L | 5.58±0.74 | 3.99±0.56 |
| FVC % pred | 100±9.0 | 101±9.4 |
| FEV1/FVC | 78.9±4.9 | 79.8±5.2 |
| FEF25 L·s−1 | 8.50±1.56 | 6.10±1.13 |
| FEF25¶ % pred | ||
| FEF50 L·s−1 | 4.87±1.22 | 3.67±0.91 |
| FEF50¶ % pred | ||
| FEF75 L·s−1 | 1.63±0.63 | 1.25±0.54 |
| FEF75 % pred | 101±29.7 | 96±30.2 |
| FEF25–75 L·s−1 | 4.03±1.10 | 3.03±0.86 |
| FEF25–75 % pred | 96±22.3 | 92±20.5 |
Data are presented as n or mean±sd. Predicted values are according to the Global Lung Initiative (GLI) equations [13]. BMI: body mass index; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; FEFx: forced expiratory flow at 25%, 50%, 75% or 25–75% of FVC. #: age range (interquartile range) 18–80 (34–49) years and 18–85 (33–48) years for males and females, respectively; ¶: no reference equations available from the GLI. For characteristics of internal and external validation sets see supplementary table S2.