Introduction: We present 5 cases where workers had been removed from the workplace because of their asthma and were prevented from returning to normal duties without proof that work was not the cause.Methods. All workers lacked prior physiological evidence of OA. Workplace challenge tests were carried out with either a control day in hospital or at home. A clinical scientist escorted the worker at their place of work on the second day. The challenge lasted up to 4 hours with the worker subjected to usual exposures. FEV1 measurements were then continued away from exposure until bed. Where possible, a non-specific bronchial provocation test was carried out before and after the workplace challenge.Results. All 5 workplace challenge tests were negative. The negative tests led to a return to normal duties after reports were sent to the occupational health or employer with the worker's consent. Following return to work serial PEF records analysed by the Oasys software showed possible OA in 1 worker. Details are shown in Table 1.

Table 1.
Case numberAgentMonths off workFEV1 % predTreatmentPD20 pre/post challenge (unexposed /exposed)
1MWF887ICS + LABANeg/Neg
2welding fume777ICS +LABA + LAMAND/ND
3isocyanates5109ICS +LABANeg/Neg
4emulsion paint7102NilNeg/ND
5floor tile adhesive12100ICSNeg/Neg
Conclusion: Workplace challenge tests not only provide a diagnosis of OA but can also be used to refute the workplace association with asthmatic symptoms and lead to a return to work with substantial cost savings. Workers should be monitored using serial PEF on return to work as the exposure time may have not been long enough to elicit a reaction.
ND=Not done