Moore, Vicky Clare (2010)
Ph.D. thesis, University of Birmingham.
Serial peak expiratory flow measurements (PEF) are recommended as an initial investigation in the confirmation of occupational asthma. Plotting measurements in Oasys gives reproducible results and can be used by non-experts. I report a new analysis, the area between curves (ABC) score, which gives 72% sensitivity and 100% specificity using a cut off of 15 L/min/h. Two-hourly measurements of PEF require 8 work days and 3 rest days for sensitive and specific analysis. Serial PEF records with long periods off work (≥ 4 consecutive days) show improved sensitivity from 73% to 80%, implying that 7 more workers in every 100 would be diagnosed. In a comparison of forced expiratory volume in one second (FEV1) to PEF, PEF was more sensitive to diurnal changes than FEV1, although FEV1 was more reproducible. Exhaled breath nitric oxide (FENO) showed similar ABC scores between those with normal and raised FENO. FENO was significantly correlated to methacholine reactivity. In shift workers, mean ABC scores were increased on morning shifts compared to nights, but the cut off of 15 L/min/h would be applicable across all shift types. The ABC score is a new robust method of confirming occupational asthma requiring shorter records than the Oasys score.
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