29% have occupational asthma when specific challenges are negative

This is one of the few studies which has attempted to investigate the sensitivity of specific challenge testing carried out in a national reference centre. 99 workers with a good history of occupational asthma had workplace challenges where a >20% fall in FEV1 was considered positive. If 1-2 days at work showed no significant reaction, peak flow recordings for 2 weeks was carried out with repeat NSBR afterwards. Of 99 workers with negative challenges 22 had a positive workplace challenge and a further 7 a positive 2-week challenge. The total numbers investigated with a positive challenge is not given in the paper, but the probility of occupational asthma in a worker with a good history and a negative secific challenge was 29%. If only those without an eventual diagnosis of asthma or rhinitis are included, 29/55 had positive workplace challenges (Rioux 2008).

References

	Rioux J-P, Malo J-L, LArcheveque J, Rabhi K, Labrecque M, Workplace-specific challenges as a contribution to the diagnosis of occupational asthma, Eur Respir J, 2008;32:997-1003,

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