Table 1

Respiratory symptomatology, spirometry and bronchial challenge test results

n/total n (%)BaselineEnd of studyMean differencep‐value
Baseline non‐W‐R RS34 (17.5)
W‐R RS at 1st follow-up12/187 (6.4)
W‐R RS at end of study14/193 (7.3)
W‐R RS at 1st follow-up and/or end of study#24/194 (12.4)
Persistent W‐R RS14/184 (7.6)
FEV1 L·min−14.35±0.874.01±0.84−0.34± 0.35<0.01+
FEV1 % pred106.48±15.6898.05±15.88−8.44±9.19<0.01+
FVC % pred103.82±21.7697.18±14.16−7.80±15.18<0.01+
FEV1/FVC % pred100.32±8.18101.54±7.53+0.99±5.320.01+
Log slope1.55±0.521.64±0.550.09±0.31<0.01+
FEV1 % pred <80% n (%)73.62211.3<0.01§
FEV1/FVC % pred <85% n (%)94.842.1ns
PC20 ≤8 mg·mL−1 n (%)2814.43618.6<0.05§
PC20 ≤16 mg·mL−1 n (%)3920.14623.7ns
  • 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