Figures
- FIGURE 1
Overview of subject selection from the Lifelines dataset. BMI: body mass index.
- FIGURE 2
Variability in the adjusted forced expiratory flows (FEFs) for a) males and b) females, per datasets. FVC: forced vital capacity; FEFx: FEF at 25%, 50%, 75% and 25–75% of FVC.
Tables
- TABLE 1
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.
- TABLE 2
Overview of adjusted forced expiratory flow (FEF) for all groups
Male Female Subjects 4846 6736 FEF25/FVC s−1 1.54±0.30 1.54±0.29 FEF50/FVC s−1 0.88±0.21 0.92±0.21 FEF75/FVC s−1 0.29±0.11 0.31±0.12 FEF25–75/FVC s−1 0.72±0.19 0.76±0.19 Data are presented as n or mean±sd. FEFx: forced expiratory flow at 25%, 50%, 75% or 25–75% of forced vital capacity (FVC).
- TABLE 3
Coefficient of variation for adjusted and unadjusted forced expiratory flows (FEFs)
Adjusted FEFx/FVC
coefficient of variation %Unadjusted FEFx coefficient of variation % p-value Males FEF25 19.2 18.3 0.00027 FEF50 23.9 25.1 0.00097 FEF75 36.0 38.7 5.81×10−5 FEF25–75 25.4 27.2 6.23×10−7 Females FEF25 18.7 18.6 0.739 FEF50 22.9 24.9 1.24×10−13 FEF75 39.8 43.2 1.51×10−10 FEF25–75 25.8 28.6 9.46×10−19 FEFx: forced expiratory flow at 25%, 50%, 75% and 25–75% of forced vital capacity (FVC).
- TABLE 4
Generated reference equations for adjusted forced expiratory flow (FEF) values
Equations Explained variance for the FEF/FVC equations % Reference equation RSD Training Internal validation External validation Males FEF25/FVC s−1 3.56+0.001A+0.003W−0.013H 0.286 6.79 6.48 13.16 FEF50/FVC s−1 2.02−0.004A+0.001W–0.006H 0.205 6.17 4.76 4.04 FEF75/FVC s−1 0.68−0.005A–0.0009W–0.0005H 0.084 35.9 32.1 37.8 FEF25–75/FVC s−1 1.70−0.007A+0.0005W−0.004H 0.169 16.6 13.8 14.9 Females FEF25/FVC s−1 3.52−0.0005A+0.003W−0.013H 0.278 6.21 5.82 4.56 FEF50/FVC s−1 2.05−0.005A+0.001W−0.006H 0.201 8.64 9.54 9.32 FEF75/FVC s−1 0.73−0.006A−0.001W−0.0004H 0.095 41.0 41.5 46.0 FEF25–75/FVC s−1 1.76−0.008A+0.00009W−0.004H 0.170 23.6 24.1 25.2 FVC: forced vital capacity; RSD: residual standard deviation; FEFx: forced expiratory flow at 25%, 50%, 75% and 25–75% of FVC; A: age (years); W: weight (kg); H: height (cm). Lower limit of normal=value−1.64×RSD; upper limit of normal=value+1.64×RSD.
- TABLE 5
Generated reference equations unadjusted forced expiratory flow (FEF) values
Equations Explained variance for the unadjusted FEF equations % Reference equation RSD Training Internal validation External validation Males FEF25 L·s−1 0.50−0.021A+0.019W+0.040H 1.478 9.73 12.1 11.6 FEF50 L·s−1 0.14−0.038A+0.008W+0.031H 1.099 19.5 19.8 20.7 FEF75 L·s−1 0.14−0.034A−0.005W+0.018H 0.469 46.8 44.7 55.0 FEF25–75 L·s−1 0.37−0.048A+0.003W+0.029H 0.903 32.6 31.9 39.2 Females FEF25 L·s−1 1.21−0.026A+0.015W+0.029H 1.039 15.6 17.0 15.4 FEF50 L·s−1 0.51−0.033A+0.007W+0.024H 0.778 27.1 27.7 29.8 FEF75 L·s−1 0.35−0.028A−0.005W+0.014H 0.375 51.4 52.0 56.8 FEF25–75 L·s−1 0.74−0.041A+0.0015W+0.023H 0.654 42.3 42.6 44.1 RSD: residual standard deviation; FEFx: forced expiratory flow at 25%, 50%, 75% and 25–75% of forced vital capacity; A: age (years); W: weight (kg); H: height (cm). Lower limit of normal=value−1.64×RSD; upper limit of normal=value+1.64×RSD.
- TABLE 6
Percentage of explained variance of existing reference equations on our datasets
Males Females Training Internal validation External validation Training Internal validation External validation Quanjer [12] FEF25 L·s−1 8.49 10.1 7.01 14.5 15.6 11.2 FEF50 L·s−1 19.1 19.3 18.0 26.7 27.4 27.6 FEF75 L·s−1 43.4 43.0 55.1 50.9 51.3 56.3 FEF25–75 L·s−1 32.3 30.6 37.2 41.9 42.3 42.1 GLI [13] FEF75 L·s−1 47.4 46.3 55.1 53.0 53.6 58.3 FEF25–75 L·s−1 32.8 32.0 38.2 42.5 42.7 42.9 Data are presented as %. FEFx: forced expiratory flow at 25%, 50%, 75% and 25–75% of forced vital capacity.
Supplementary Material
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Supplementary material 00426-2020.SUPPLEMENT
