Occupational Asthma Reference

Fishwick D, Bradshaw LM, Tate PA, Curran AD, Occupational asthma evaluation, Thorax, 2003;58:461,


Known Authors

Andrew Curran, HSL, Sheffield, UK Andrew Curran

David Fishwick, Royal Hallamshire Hospital, Sheffield, UK David Fishwick

Lisa Bradshaw, Health and Safety Laboratories Lisa Bradshaw

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We read with interest the paper by Baldwin et al on the level of agreement between expert clinicians and OASYS software when making a diagnosis of occupational asthma. Our clinical unit uses OASYS plotting regularly, and finds it of great use as one element of the diagnostic toolkit available for the confirmation of a diagnosis of occupational asthma.

We were interested to note that there was a low level of agreement between experts and OASYS when peak expiratory flow (PEF) records were interpreted, but agreement within experts was better. We would be interested to know whether the information provided to the experts on the nature of the work was used in determining their final outcome—that is, if an individual was working with a known sensitiser or was in a perceived high risk job, did this influence the outcome more than the graphical and mathematical data? In the clinical setting a decision is made to perform regular PEF monitoring in those patients who are thought to have a reasonable chance of having occupational asthma, as judged by the clinical information to date. Perhaps a further study option would be to give experts the clinical data first (more like the real life situation) and ask for a likelihood of occupational asthma based on this assessment, followed by a revision of that likelihood after PEF data are supplied. Would revealing the work effect score lead to further revision of the perceived estimate? Individual experts may be more or less swayed by the clinical data due to variation in their own practice, types of cases seen, geographical location, and so on.

Experts were deemed to "under report" possible cases of occupational asthma. While this may indeed be the case, an alternative explanation is that the experts were more realistic, taking into account the clinical likelihood as well as the PEF pattern. OASYS systems clearly invoke complex comparisons between known cases of occupational asthma and the record being assessed. The authors suggest that PEF interpretation is best left to experts. While we agree that expert centres which consistently diagnose occupational asthma are needed, as many as one in 10 adult asthmatic patients is likely to have a substantial effect from work. It is therefore important for all such patients in the UK to have access to competent individuals trained to assess these patients. This is where OASYS (or similar) systems are likely to be very important as an initial screen, and could be carried out by primary care or occupational health nurses or other competent non-clinical people in the workplace. This would enable patients currently working to undergo PEF assessment, as opposed to the common situation of seeing patients in secondary care following a prolonged period of sickness absence, making diagnosis even more challenging.

At present the consistency of diagnosis of occupational asthma throughout the UK is likely to be highly variable. We are currently involved in a multicentre UK based study assessing the application of the toolkit to diagnose occupational asthma, and it is evident that practice remains disparate between various expert centres.

We are sure that the future of occupational asthma evaluation will and should rely on programs like OASYS, but that the diagnosis must be seen also in broader terms, taking into account clinical, immunological, and exposure data.

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