Occupational asthma should be suspected in all adult patients with asthma.
An occupational history should be taken to identify work-related causes. Details of work exposures should be obtained from material safety data sheets and other material available to the patient from their workplace.
Objective evidence of asthma should be obtained from spirometry, a bronchodilator response, and/or a methacholine challenge. Tests should be performed when the patient is symptomatic and/or within days of having exposure to a suspected aetiological agent.
If sensitiser-induced occupational asthma is suspected, additional testing of asthma should be done, preferably while the patient is still working. Whenever possible an immunological response to a suspected work sensitiser should be demonstrated by skin or in vitro tests.
Where possible, an early diagnosis based on as much objective data as is available should be made.
In sensitiser-induced occupational asthma, removal from any further exposure to that agent should be recommended.
In irritant-induced occupational asthma, preventive measures should be implemented in the workplace to reduce future exposures and episodes.
For all causes of occupational asthma, the clinician should continue treating the asthma as appropriate, assist in the initiation of any appropriate compensation claim, and consider other workers at risk.
Occupational asthma (OA) is asthma caused by the workplace and may result from immunological or non-immunological stimuli. There are 2 main forms. Sensitiser-induced OA is caused by immunological stimuli and develops after a latency period between first exposure and the onset of symptoms. Irritant-induced OA (including reactive airways dysfunction syndrome) is caused by non-immunological stimuli.
History and exam
Key diagnostic factors
- presence of risk factors
- occupational exposure to sensitising agents or irritants
- symptoms of asthma that improve during holidays
- initial onset of asthma symptoms during a work period
- high-level exposure to sensitiser
- genetic factors
1st investigations to order
- spirometry (pre- and post-bronchodilator)
- chest x-ray
- skin prick testing
- specific serum IgE assay
- non-specific bronchial provocation testing
- serial peak expiratory flow rate
Investigations to consider
- specific inhalation challenge
- induced sputum cytology
- exhaled nitric oxide
- Work-exacerbated asthma
- Occupational eosinophilic bronchitis
- Coincidental non-occupational asthma
- Global strategy for asthma management and prevention
- Japanese guidelines for occupational allergic diseases 2020
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