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Occupational asthma
S160 The effect of shift work on serial peak expiratory flow measurements used to diagnose occupational asthma
  1. V C Moore1,
  2. M S Jaakkola2,
  3. C B S G Burge1,
  4. C F A Pantin3,
  5. A S Robertson1,
  6. P S Burge1
  1. 1Birmingham Heartlands Hospital, Birmingham, UK
  2. 2Oulu University, Oulu, Finland
  3. 3University Hospital of North Staffordshire, Stoke on Trent, UK

Abstract

We investigated the effects of shift work on Peak Expiratory Flow (PEF) measurements used for diagnosing occupational asthma (OA). In a clinic database of workers investigated for OA, 123 workers with OA and 69 workers without OA had PEF records containing >1 shift pattern with ≥4 days on each shift. The OA definition was based on Oasys-2 score >2.51 and the non-OA on an alternative clinical diagnosis and Oasys-2 score <2.51. Records not fulfilling the minimum data quantity for the Area Between Curves (ABC) PEF score, or containing respiratory infections, changes in asthma treatment or different exposures on each shift were excluded. The mean ABC score, mean PEF diurnal variation (DV) on workdays and cross-shift PEF changes were calculated for each shift. The ABC score of the OA workers was lower on nights (p=0.028) and afternoons (p=0.020) compared to day shifts, without significant differences in diurnal variation. There was statistically significant difference between day and night shift cross-shift changes (p<0.001), larger changes being observed in nights. The sensitivity and specificity of the ABC score was 79% and 99% for day shifts, 83% and 98% for nights and 72% and 96% for afternoon shifts. The sensitivity of increased DV on work days compared to rest days was 76% for day shifts, 78% for nights and 70% for afternoons, specificities being 26%, 48% and 42%, respectively. PEF changes between work and rest show small differences with shift types. The ABC score has high sensitivity and specificity for all three shifts; differences in DV have high sensitivity, but low specificity when using a cut-off point of >0% for the difference between work and rest day DV.

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