ABSTRACT

1. The effect of shift work on serial peak expiratory flow measurements used to diagnose occupational asthma MOORE VC, JAAKKOLA MS, BURGE CBSG, PANTIN CF, ROBERTSON AS AND BURGE PS Occupational Lung Disease Unit, Birmingham Heartlands Hospital, UK ABSTRACT RESULTS 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 ≥four 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 3 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. ID = OA diagnosis based on independent confirmatory tests OA = Occupational asthma Mean rest day diurnal variation for all occupational asthma subjects (n=123) was11.4 (SD 7.7) and for non occupational asthma subjects (n=69) 9.9 (SD 5.3) SENSITIVITY & SPECIFICITY AIMS CONCLUSIONS EXAMPLE SERIAL PEF • To investigate whether shift work pattern alters the PEF responses to occupational exposures METHODS • On average, the ABC score is significantly smaller during night shifts compared to day shifts. • DV showed no significant changes between shifts • Cross shift differences were less on day shifts compared to afternoon or night shifts. • Detailed analysis shows there are those who are worse on nights compared to days, those who are similar on all shifts and those who are better on nights compared to days. • A cut off of 15L/min (found previously for day shifts only) is likely to be appropriate for all shift types. • Sensitivity and specificity is good for all shift types using the ABC score, DV specificity is low. • Serial PEF records from workers with occupational asthma (OA) and those with alternative diagnoses searched for on our PEF database • Records were required to have at least 4 days of at least 2 shift patterns (morning, afternoon and night) • Only records with minimum data amounts for the ABC score / cross shift changes were used • Records with respiratory tract infections, treatment changes or known differences in exposure between shift types removed • Cross shift PEF difference, ABC score and DV changes for each shift type were analysed • Sensitivity and specificity against the Oasys score calculated • SPSS 15 used for all statistical analyses Visit our website: www.occupationalasthma.com