[Is the bronchial provocation test justified in occupational respiratory disease?]

Specific bronchial provocation tests can confirm the diagnosis of occupational respiratory disease and also identify the causal agent of occupational asthma. The changes in French regulations established in 1993 which allow other agents to be recognized as causal in compensation for occupational diseases has increased interest in these tests. The different diagnostic methods used for occupational asthma are discussed here with special emphasis on limitations in each case: history taking, immunological investigations, respiratory function tests, measurement of peak flow during occupational activity and holidays, sequential measurements of non-specific bronchial hyperreactivity. The difficulty in standardizing specific provocation tests used for occupational asthma is related to the wide variety of causal agents which can be inhaled as gas, aerosols or powders. Because of the required precautions, these tests must be performed by specialized personnel in hospital units. There are also limitations to specific provocation tests. False positives require placebo tests and false negatives may result from insufficient identification of the causal agent. Exposure time may be too short or concentrations too low, and may depend on how long the causal agent has been evicted. Specific provocation tests may be avoided when the clinical history reveals a typical situation due to an agent known to cause occupational asthma and repeated peak flow measurements at the working site and/or immunological sensitisation tests provide objective evidence. But in a certain number of cases, specific investigations are required to obtain the precise etiological diagnosis required to evict the allergen rapidly and avoid chronic asthma.