Respiratory symptomatology, spirometry and bronchial challenge test results
| n/total n (%) | Baseline | End of study | Mean difference | p‐value | |
| Baseline non‐W‐R RS | 34 (17.5) | ||||
| W‐R RS at 1st follow-up | 12/187 (6.4) | ||||
| W‐R RS at end of study | 14/193 (7.3) | ||||
| W‐R RS at 1st follow-up and/or end of study# | 24/194 (12.4) | ||||
| Persistent W‐R RS¶ | 14/184 (7.6) | ||||
| FEV1 L·min−1 | 4.35±0.87 | 4.01±0.84 | −0.34± 0.35 | <0.01+ | |
| FVC | 5.09±0.98 | 4.67±0.93 | −0.43±0.42 | <0.01+ | |
| FEV1 % pred | 106.48±15.68 | 98.05±15.88 | −8.44±9.19 | <0.01+ | |
| FVC % pred | 103.82±21.76 | 97.18±14.16 | −7.80±15.18 | <0.01+ | |
| FEV1/FVC % pred | 100.32±8.18 | 101.54±7.53 | +0.99±5.32 | 0.01+ | |
| Log slope | 1.55±0.52 | 1.64±0.55 | 0.09±0.31 | <0.01+ | |
| FEV1 % pred <80% n (%) | 73.6 | 22 | 11.3 | <0.01§ | |
| FEV1/FVC % pred <85% n (%) | 94.8 | 4 | 2.1 | ns | |
| PC20 ≤8 mg·mL−1 n (%) | 2814.4 | 36 | 18.6 | <0.05§ | |
| PC20 ≤16 mg·mL−1 n (%) | 3920.1 | 46 | 23.7 | ns |
Data are presented as mean±sd, unless otherwise stated
n=194
A total 92 apprentices did not have the methacholine bronchial challenge test (82 dropped out, eight refused to do the test and two students did not do the test at visit 1)
W‐R: welding-related
RS: respiratory symptoms
FEV1: forced expiratory volume in one second
FVC: forced vital capacity
NS: nonsignificant
PC20: provocative concentration causing a 20% fall in the FEV1
#: cases include subjects that developed at least one W‐R RS suggestive of occupational asthma (OA) at least once during the study
¶: cases include subjects that developed at least one W‐R RS suggestive of OA at first follow-up that persisted until the second follow-up or the development of at least one W‐R RS as of the second follow-up
+: p‐value in a paired-samples t‐test
§: p‐value in a McNemar test
n=194