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Asthma - Management
Suspected occupational asthma: How do I manage?
- Refer any individual with suspected occupational asthma to a respiratory specialist for confirmation.
- Suspect occupational asthma in adults who developed asthma in adulthood or have a recurrence of childhood asthma and have:
- Asthma symptoms that are better on days away from work or on holidays.
- A high-risk occupation, such as paint sprayers, bakers and pastry makers, nurses, chemical workers, animal handlers, welders, food processing workers, and timber workers.
- Ask the person to keep a peak flow diary, recording their peak flow at work and away from work to show the specialist.
Clarification / Additional information
- Work-aggravated asthma occurs when pre-existing asthma is aggravated by non-specific dust or fumes at work. In contrast, occupational asthma is pre-existing asthma which becomes additionally sensitized to an occupational agent.
- Refer people with suspected occupational asthma to the occupational health service at the workplace (if available) or a respiratory specialist.
- Occupational asthma is diagnosed in secondary care when all the following are true:
- The diagnosis of asthma is confirmed.
- A relationship between asthma and work exposures is confirmed, for example, by:
- Serial measurements of peak expiratory flow rate at home and at work (at least three series of consecutive days at work with three periods away from work, at least four evenly spaced readings per day, and at least 3 days in each consecutive work period).
- Specific and non-specific bronchial provocation tests.
- A specific cause is identified.
- Following confirmation, the person should relocate away from exposure as soon as possible, and ideally within 12 months of the first work-related symptoms of asthma. Sometimes, substitution of the hazard may be an alternative option.
- Children may be affected by occupational allergens brought home by their parents.
- More information and a computer tool for analysing data are available from www.occupationalasthma.com.
Basis for recommendation
- These recommendations are based on the British Guideline on the Management of Asthma: a national clinical guideline [SIGN and BTS, 2009]:
- The aim of management is to identify the cause, to remove the worker from exposure, and for the person to have worthwhile employment. Early identification and avoidance of the exposure offers the best chance of complete recovery. Studies have shown that the prognosis is worse for people who remain exposed after 1 year of symptoms compared with those removed earlier.
- History: asking about symptoms improving away from work is more sensitive than asking about worsening symptoms at work, as many symptoms deteriorate in the hours after work or during sleep. However, these questions are not specific for occupational asthma and also identify people with asthma due to agents at home (who may improve on holidays) and those who do much less physical activity away from work (exercise-induced asthma).
- Investigations: serial peak flow measurements are the most sensitive and specific initial investigation. Lung function tests away from work may have false-negative results. Specific bronchial provocation testing is the gold standard, but few facilities in the UK do such testing. Most cases of occupational asthma can be diagnosed in secondary care without such a test.
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