2nd Jack Pepys Occupational Asthma Workshop

1. 2nd Jack Pepys Occupational Asthma Workshop Definitions * * Based on : Vandenplas O, Malo JL. Definitions and types of work-related Asthma: a nosological approach. Eur Respir J 2003; 21:706-712

2. Rationale • Definitions vary with time : evidence, diagnostic means 2. Definitions vary according to purposes : epidemiology, surveillance programs, clinical, medicolegal, etc. • “ Nevertheless, in the same way as the existence of a consensus definition of asthma has improved its recognition and management in recent years, precise and workable definitions of OA and other types of work-related asthma are required to improve the investigation and management of these common conditions.” (Vandenplas O, Malo JL)

3. Historical proposal “Having made a diagnosis of asthma (‘widespread airways obstruction reversible over short periods of time, either spontaneously or as a result of treatment’) it is then necessary in occupational asthma to establish a relationship to the work as recommended by Ramazzini in 1713” Pepys J. Occupational asthma: review of present clinical and immunologic status. J Allergy Clin Immunol 1980;66:179-85.

4. Proposals "Occupational asthma is variable airways narrowing causally related to exposure in the working environment to airborne dust, gases, vapours or fumes. … Such findings fulfil the classical clinical criteria of hypersensitivity …" Newman Taylor AJ. Occupational asthma. Thorax 1980;35:241-5.

5. Proposals "Occupational asthma, therefore, is caused by some specificagent or agents in the form of dust, fumes or vapours in an industrial environment" Parkes WR. In: Occupational lung disorders. London: Butterworths; 1982. p. 415-53.

6. Proposals "Occupational asthma will be defined as asthma caused by specific agents in the workplace. This will excludebronchoconstrictions induced by irritants at work, exercise and cold air." Chan-Yeung M, Malo JL. Occupational asthma. Chest 1987;91:130S-6S.

7. Proposals "Occupational asthma is asthma which is due in whole or in part to agents met at work. Once occupational sensitisation has occurred… " Burge PS. Occupational asthma. In: Barnes P, Rodger IW, Thomson WNC, editors. Asthma: Basic mechanisms and clinical management. London: Academic Press; 1988. p. 465-82.

8. Proposals "Occupational asthma is a disease characterised by variable airflow limitation and/or airway hyperresponsiveness due to causes and conditions attributable to a particular occupational environment and not to stimuli encountered outside the workplace.” Editors of Asthma in the Workplace, 2nd ed., 1999

9. Agent specific to the workplace : What does “specific” mean ? Distinction with “non-specific” agents ? Sensitizing mechanism : Immunological sensitization ? Is the mechanism of irritant-induced asthma immunological ? Causalrelationship : Differences between “inducers” and “inciters” : “inducers” cause airway obstruction, hyper- responsiveness and inflammation, more or differently so than “inciters”…

10. Asthma in the Workplace Asthma caused by the workplace (occupational asthma) Asthma exacerbated by the workplace Asthma-like conditions ex: eosinophilic bronchitis With a latency period Without a latency period Irritant-induced asthma or Reactive airways dysfunction syndrome

11. Vandenplas O, Malo JL. 2003

12. Relevance of distinguishing between asthma caused by the workplace and work-exacerbated asthma Frequency : “gap” - 5 to 10% of adult-onset asthmatic subjects report that their asthma in worse at work - incidence of occupational asthma : Québec: 2/100 000 workers / yr 2. Pathophysiological mechanisms 3. Management 4. Long-term consequences when removed from exposure

13. Issues and Controversies Occupational asthma with a latency period Confirmation of the “ causal relationship ” : changes in airway caliber ± changes in non-specific responsiveness ± airway inflammation

14. Issues and Controversies Occupational asthma without a latency period Diagnosis based on history Role of multiple exposures to low doses of irritant material What is acceptable “latency” ?

15. Issues and Controversies Work-exacerbated asthma Work-exacerbated asthma SYMPTOMS How to prove it with objective means ? How to distinguish it from occupational asthma with a latency period ?

16. Conclusion “Considering the above critical review of … definitions, the keystone for defining OA is the causal relationshipbetween workplace exposure and the development of asthma. It, therefore, seems logical to limit the definition of OA to those conditions in which the asthma is induced or caused by occupation in the same way as recently proposed by a panel of experts” Vandenplas O, Malo JL., 2003

17. Conclusion “ The clinical and medico-legal definition of OA should be limited to include only those cases in which a causal relationship can be objectively established between exposure to a workplace or a substance in the workplace and the inception of asthma. Other types of asthma related to the workplace environment require further investigation in order to identify their characteristics and to develop evidence-based definitions.” Vandenplas O, Malo JL 2003