New guidelines for the management of occupational asthma in primary care and occupational health
Why does asthma start or recur in an adult? The cause will be work in
at least one out of every 10 adults of working age. It is hard to think
of many other causes of adult asthma; some will be caused by beta
blockers, a few by NSAID’s, and some perhaps follow an acute
respiratory illness or a large irritant exposure. When work is the
cause, it affects your patient’s livelihood as well as their health.
This month sees the publication of full evidence based guidelines for
the management of patients with occupational asthma . The guidelines
supplement the recent SIGN/BTS asthma guidelines
, which did not extend the evidence review to occupational asthma.
The guidelines were sponsored by BOHRF (British Occupational Health
Research Foundation), a charity sponsoring research
of practical value in occupational health (including recent guidelines
which improve the management of workers with low back pain) .
Occupational asthma is the commonest occupational lung disease in
westernised countries. All primary care health professionals are likely
to have affected patients, who will often see their General
Practitioner (GP) or Practice Nurse as their first medical contact. All
family practices should be able to screen for occupational asthma, and
have a plan
for further management.
Occupational asthma tends to occur in clusters. Spray painters,
bakers, nurses, chemical workers, animal handlers, food processors,
welders and timber workers are amongst those at highest risk. The most
common causes are isocyanates, flour, grain, colophony, fluxes, latex,
animals, aldehydes, welding fume and wood dusts, although cases can
occur almost anywhere.
All is not well in the management of patients with occupational
asthma. The diagnosis is frequently delayed for many years, increasing
the likelihood of long-term disability. Expert opinion is often hard to
find. Approximately one third of patients are unemployed up to 6 years
after diagnosis . There is good evidence that early detection and
from exposure improves prognosis, but that leaving work often leads to
substantial loss of income. The best solution is to modify the
workplace. If a doctor or nurse developed latex asthma would you expect
them to be told to leave their job? Do we advise spray painters, master
bakers or welders any differently? Many nurses and a few doctors have
developed severe latex allergy, to the extent that they cannot enter
healthcare premises without exacerbating their asthma. Once identified,
affected individuals can be relocated to areas without latex
gloves. Cornstarch used to powder gloves acts as
a carrier for the latex allergen. Removing powder
from latex gloves reduces the airborne latex levels preventing further
workers from developing latex induced asthma and permitting some
asthmatic patients to return to the workplace. There remains further
scope for substituting latex for less allergenic materials in medical
Screening for occupational asthma is easy. All
adult asthmatics should be asked whether their
symptoms improve on days away from work or on
holiday. Few cases are missed by these questions,
but they lack specificity i.e. they pick out many
who do not have occupational asthma. Further confirmation is needed before important life decisions
are made. The BTS/SIGN guidelines  recommend
specialist referral for these patients; some countries, for example the United Kingdom do not have
many specialists in occupational lung diseases.
Occupational-style serial measurements of peak
expiratory flow are possible in primary care, but
require enthusiasm and attention to detail. The
aim is to see if occupational exposure provokes the
asthma. Once occupational asthma has developed,
the peak expiratory flow will be influenced by waking time (often earlier on workdays), treatment
and other provoking factors such as exercise and
cold air. The guidelines recommend measurements
at least 4-times daily (or even better two-hourly),
over 4 weeks with daily recording of waking and
sleeping times, and times starting and stopping
work. Diagnostic records are best made before
treatment is increased and workplace modifications
made. Once recorded they need to be analysed by
an expert. Advice and record forms are available on
the website http://www.occupationalasthma.com
. This site also has links to the full guidelines
. Other means of confirmation include immunological and challenge tests, which require referral
to a specialist.
The best outcomes leave a worker employed and without exposure to
the causative agent within a year of the first work-related symptom.
GP’s should not recommend patients to leave their employment as a means
of avoiding exposure, except as a last resort. This leaves an
unemployed patient who is likely to have problems with re-employment,
and will minimize the chances of remedial action in the workplace.
Having obtained patient consent the employer should be told of the
agent that your patient needs to avoid. The employer should also take
steps to prevent further cases. This clearly needs
an accurate diagnosis which often requires specialist referral;
specialists should also be able to advise on compensation issues.
- Newman Taylor AJ, Nicholson PJ (Editors). Guidelines for the
prevention, identification and management of occupational
asthma: Evidence reviewand recommendations. British Occupational Health Research Foundation, London 2004.
- British Thoracic Society; Scottish Intercollegiate Guidelines
Network. British guideline on the management of asthma.
Thorax 2003: 58 Suppl 1:i1-94. (no longer available on the web as far as we know.)
- Carter JT, Birrell LN (Editors). Occupational health guidelines for
the management of low back pain at work - principal recommendations.
Faculty of Occupational Medicine. London. 2000 www.facoccmed.ac.uk/library/index.jsp?ref=383
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