Reference

Gautrin D, InfanteRivard C, Ghezzo H et al, Incidence and host determinants of probable occupational asthma in apprentices exposed to laboratory animals, Am J Respir Crit Care Med, 2001;163:899-904,

BOHRF Original Authors' Main Conclusions

The original authors' main conclusions are taken from Abstract, Results and Discussion. They are decided upon by the authors of the BOHRF occupational asthma guidelines and form part of the guidelines.

Pre-exposure host characteristics and the school attended were compared between cases and all cohort subjects not meeting the criteria for probable occupational asthma. Twenty-eight apprentices satisfied the definition for 'probable occupational asthma', i.e., onset of immediate skin reactivity to > 1 occupational inhalant and > 3.2-fold decrease in the provocative concentration causing a 20% reduction in FEV1 (PC20). The incidence of 'probable occupational asthma' was 2.7%. Baseline immediate skin reactivity to pets (rate ratio [RR] 4.1, 95% and bronchial responsiveness (PC20 = 32 versus PC20 > 32 mg/ ml) (RR = 2.5) were associated with an increased risk of probable occupational asthma; a lower FEV1 had an apparent, protective effect (RR = 0.58). Authors conclude that apprentices in animal health show a high incidence of probable occupational asthma, and that pre-exposure airway calibre and responsiveness as well as sensitisation to pets are associated with an increased risk. In the comparison of probable occupational asthma cases with subjects with incident sensitisation and no decrease in bronchial responsiveness, only immediate skin reaction to pets was significantly associated with the risk of probable occupational asthma, and a lower FEV1 had an apparent protective effect for the incidence of probable occupational asthma. In the third comparison, atopy, immediate skin reaction to pets, and rhinitis on contact with pets significantly increased the risk of developing probable occupational asthma, whereas having a lower FEV1 was associated with a decreased risk. Of 78 apprentices identified prospectively as developing immunological sensitisation, 36.9% developed probable occupational asthma; therefore, the development of IgE-dependent immunological sensitisation results in a high risk of having probable occupational asthma in the case of animal-derived allergens. This study adds some evidence that asthma is not a risk factor for the incidence of 'probable occupational asthma', and also suggests that having a high FEV1 does not preclude the development of 'probable occupational asthma'.

BOHRF Associated Evidence Statements

The BOHRF occupational asthma guidelines state that this reference is associated with the following evidence statements

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Atopy increases the risk of developing occupational asthma caused by exposure to many high molecular weight agents that induce the production of specific IgE antibodies.

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Occupational rhinitis and occupational asthma frequently occur as co-morbid conditions in IgE associated occupational asthma.

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Rhino-conjunctivitis is more likely to appear before the onset of IgE associated occupational asthma.

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Sensitisation and occupational asthma are most likely to develop in the first years of exposure for workers exposed to enzymes, complex platinum salts, isocyanates and laboratory animal allergens.

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A previous history of asthma is not significantly associated with occupational asthma.