Table 2.
Baseline spirometric measures of the included participants
| Variable | Total n=1458 |
Normal FEF25-75/AL− n=316 |
Low FEF25-75/AL− n=335 |
Low FEF25-75/AL+ n=806 |
| FEV1 | ||||
| z-score | −2.09 (−3.16 to −1.11) | −0.44 (−1.00 to 0.20) | −1.67 (−2.26 to −1.18)* | −2.97 (−3.70 to −2.12)*† |
| % predicted | 67.05 (47.65 to 84.12) | 93.68 (85.60 to 103.92) | 74.05 (64.50 to 82.43)* | 50.91 (37.25 to 66.36)*† |
| FVC | ||||
| z-score | −0.50 (−1.15 to 0.20) | −0.50 (−1.15 to 0.20)†‡ | −1.34 (−2.02 to −0.63) | −1.19 (−2.02 to −0.35) |
| % Predicted | 84.43 (71.96 to 96.75) | 93.16 (83.37 to 103.37)†‡ | 80.44 (70.60 to 91.37) | 82.05 (69.22 to 95.38) |
| FEV1/FVC ratio§ | ||||
| z-score | −1.93 (−3.34 to −0.63) | 0.09 (−0.30 to 0.46) | −1.00 (−1.33 to −0.60)* | −3.18 (−4.11 to −2.34) |
| % | 63 (48 to 74) | 79 (76 to 83) | 71 (68 to 75)* | 50 (39 to 59) |
| FEF25-75§ | ||||
| z-score | −1.96 (−2.80 to −1.01) | −0.16 (−0.49 to 0.25) | −1.37 (−1.67 to −1.11) | −2.72 (−3.2 to −2.18)† |
| % Predicted | 40.56 (21.08 to 67.58) | 95.25 (83 to 110.51) | 56.02 (47.76 to 63.70) | 22.74 (14.80 to 33.76)† |
| FEF25-75/FVC ratio | 48.28 (27.25 to 79.86) | 104.80 (90.10 to 122.99) | 68.02 (59.16 to 79.86)* | 28.73 (19.90 to 40.47)*† |
| FEV3/FVC ratio | 85.44 (74.22 to 92.26) | 94.65 (92.10 to 96.83) | 90.75 (87.73 to 93.46)* | 75.13 (64.70 to 82.67)*† |
Data are presented as median and IQR. In the groups’ comparisons, the significance level for adjusted p value was set at 0.05.
*Significantly different from normal FEF25-75/AL−.
†Significantly different from low FEF25-75/AL−.
‡Significantly different from low FEF25-75/AL+.
§Statistical test was only undertaken for differences between groups where a definition did cause the variable to differ.
AL, airflow limitation; FEF25-75, forced expiratory flow between 25% and 75% of vital capacity; FEV1, forced expiratory volume in 1 s; FEV3, FEV in 3 s; FVC, forced vital capacity.