Occupational Asthma Reference

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,

Keywords: Canada, workplace challenge, sensitivity, specific challenge,occupational asthma, diagnosis

Known Authors

Jean-Luc Malo, Hôpital de Sacré Coeur, Montreal, Quebec, Canada Jean-Luc Malo

Manon Labrecque, Hôpital de Sacre Coeur, Montreal, Quebec, Canada Manon Labrecque

Jean-Phillipe Rioux, Hôpital de Sacré Coeur, Montreal, Quebec, Canada Jean-Phillipe Rioux

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Abstract

The diagnosis of occupational asthma can be made by exposing workers to the
relevant agent either in a hospital laboratory through specific inhalation challenges (SICs) or in the workplace. As suggested by several authors, workers with negative laboratory SIC can be monitored at the workplace under supervision. The present study aims to assess the frequency of, and identify factors associated with, a positive workplace reaction in workers with negative SIC in the laboratory.

Methods
The results of workplace challenges were examined in 99 workers who underwent negative SIC between 1994 and 2004. A positive reaction either in the SIC or in the workplace was defined as a sustained fall in forced expiratory volume in one second of >20%.

Results
In total, 22 (22.2%) workers showed positive responses at the workplace. These subjects more often had increased baseline methacholine responsiveness (90.5 versus 67.6%). They also underwent more days of SIC testing (4.9 versus 3.3 days) and were exposed more often to two or more agents (56 versus 28.4%) and for a longer period of time (363.3 versus 220.4 min) in the laboratory.

Cnclusion
The present study illustrates the usefulness of workplace monitoring of airway function in the investigation of occupational asthma and identifies factors that are more often associated with a positive reaction.

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Associated Questions

Registered users of this website have associated this reference with the following questions. This association is not a part of the BOHRF occupational asthma guidelines.

What are the sensitivity and the specificity of specific bronchial provocation testing while at work, and after removal from work, in the diagnosis of validated cases of occupational asthma?
burgeps 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%

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