Occupational Asthma Reference

Labrecque M, Malo J-L, Alaoui KM, Rabhi K, Medical surveillance programme for diisocyanate exposure, Occup Environ Med, 2011;68:302-307,

Keywords: Quebec, Canada, Surveillance, cost effectiveness, compensation, isocyanate, HDI, spray painter, challenge, NSBR

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

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Surveillance programmes for occupational asthma should reduce the severity of asthma both at the time of diagnosis and after removal from exposure as well as costs related to functional impairment. The aim of this study was to compare the severity and cost of diisocyanate-induced occupational asthma in workers participating in a surveillance programme and in twice the number of workers diagnosed after being referred by their physician.

Answers to a self-administered questionnaire led to possible referral for further assessment that included methacholine testing and specific inhalation challenges as the gold standard for confirming occupational asthma.

Of the 2897 workers who participated, 182 (6.3%) had a positive questionnaire. 79/182 (43%) were referred for further medical assessment and 20 had confirmed occupational asthma by specific inhalation testing. At the time of diagnosis, the 20 screened subjects had a mean PC20 of 3.35 mg/ml as compared to 1.50 mg/ml (p=0.05) in the 66 controls. Two years after diagnosis and removal from exposure, the 20 subjects screened had a mean PC20 of 4.81 mg/ml compared to 1.67 mg/ml (p=0.03) in controls. Clinical remission occurred in 34% of the screened group compared to 16% of the control group (p=0.02). The median costs for functional impairment were $C11?900 in screened subjects and $C19?600 in controls (p=0.04).

Subjects with occupational asthma screened by a medical surveillance programme have a better outcome both at the time of diagnosis and 2 years after removal from exposure, with lower compensation costs compared to controls.

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Really a cross-sectional study at the start of a surveillance programme compared with workers diagnosed with occupational asthma presenting clinically (historical controls). Those identified by surveillance had less NSBR and recovered better than the historical controls (2 years after removal from exposure no treatment and normal NSBR 34% vs 16%, p=0.02). They also cost the Quebec compensation scheme, which includes less (11,893 Canadian $ including retraining compared with Can $19,462 for the historical controls.
The screened group had symptoms for a mean 5.2 years and had worked with isocyanates for a mean 12.9 years, representing a late onset of disease group. The figures for those actually with OA are not given.
The original screening was with questionnaire identifying 6.3% of isocyanate spray painters (n=182). Of these 103 were thought not to have OA after a medical. 79 were referred for investigation, NSBR <8mg/ml in 55/79. 20 had positive isocyanate challenges (0.69% of the original cohort).

42% of the 22 with challenge positive OA had normal NSBR (interval from last exposure not stated)
The cost comparison was the lump sum paid after 2 years by the Quebec compensation scheme based on age and residual disability. It is cheaper to identify spray painters with occupational asthma with screening than to wait for them to present clinically.

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