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7.9.6 SPECIFIC BRONCHIAL PROvOCATION TESTING
Specific provocation challenges are usually used as the gold standard for occupational asthma
diagnosis making assessments of their diagnostic validity difficult. In addition, there are no
standardised methods for many occupational agents. There is also evidence that the threshold
exposure increases with time since last exposure, making the tests less sensitive after prolonged
absence from work. There are reports of people having non-specific reactions to specific
challenges at concentrations likely to be found in the workplace or of negative reactions to
specific challenges in workers with otherwise good evidence of occupational asthma when
challenge concentrations are confined to levels below occupational exposure standards.
594,597,600,603,604
d A negative specific bronchial challenge in a worker with otherwise good evidence of
occupational asthma is not sufficient to exclude the diagnosis.
7.10 MAnAGeMent of oCCuPAtionAl AsthMA
The aim of management is to identify the cause, remove the worker from exposure, and for the
worker to have worthwhile employment.
Complete avoidance of exposure may or may not improve symptoms and bronchial hyperresponsiveness.
Both the duration of continued exposure following the onset of symptoms and
the severity of asthma at diagnosis may be important determinants of outcome. Early diagnosis
and early avoidance of further exposure, either by relocation of the worker or substitution of
the hazard offer the best chance of complete recovery. Workers who remain in the same job
and continue to be exposed to the same causative agent after diagnosis are unlikely to improve
and symptoms may worsen. The likelihood of improvement or resolution of symptoms or of
preventing deterioration is greater in workers who have no further exposure to the causative
agent. 576,605-613
Several studies have shown that the prognosis for workers with occupational asthma is worse
for those who remain exposed for more than one year after symptoms develop, compared with
those removed earlier. 614-616
d Relocation away from exposure should occur as soon as diagnosis is confirmed, and
ideally within 12 months of the first work-related symptoms of asthma.
There is consistent evidence from clinical and workforce case series that about one third of
workers with occupational asthma are unemployed after diagnosis. It is unclear whether this
risk is higher than that for other adults with asthma. 582,617,618 The risk of unemployment may fall
with increasing time after diagnosis. 619 There is consistent evidence that loss of employment
following a diagnosis of occupational asthma is associated with loss of income. Adults with
occupational asthma may find employment more difficult than adults with non-occupational
asthma. 617,618 Approximately one third of workers with occupational asthma have been shown
to be unemployed up to six years after diagnosis. 582,617-624
7 sPeCiAl situAtions
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