Using an occupational history

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Using an occupational history
Grant McMillan Hon Senior Clinical Lecturer
Institute of Occupational and Environmental
Health University of Birmingham Number 5 of a
series of lectures and tutorials for medical
undergraduates
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This is a self-help tutorial designed to provide
you with an introduction to using an occupational
history to help you determine if your patient has
an occupational disease.
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Categories of work-related diseases

• I Work the cause
• II Work a causal factor in diseases of common
  occurrence
• III Work provoking or aggravating an
  established disease
• IV Work offering ready access to potential
  dangers

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Criteria for diagnosing an occupational/work-relat
ed disease

• Effect
• Exposure
• Time sequence
• Competing causes
• Biological plausibility
• Each of these is now considered in turn

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Effect

• Describe the effect ie presence of symptoms and
  signs.
• Does this fit the case definition of an accepted
  work-related disease?
• Have you found other cases?

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Exposure

• Exposure must be sufficient to cause the disease
• From the history, occupational hygiene records
  or by monitoring determine
• What? Nature of hazard
• How much? Dose received
• Is this sufficient to cause harm?

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Exposure

• Now, compare measured or recorded dose against
  published exposure limits to determine if
  exposure could be expected to cause effects.
  Remember that some people are unusually sensitive
  to some hazardous agents.

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Time sequence

• Exposure must be prior to onset of illness.
• Immediate effects eg hydrogen cyanide
• Hours delay of effects eg phosgene, oxides of
  nitrogen, arc eye.
• Weeks or months delay of effects dermatitis,
  asthma
• For cancers - appropriate latency period

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Consider non-occupational causes

• What is differential diagnosis?
• Non-occupational causes
• Environmental
• Social (smoking, alcohol, hobbies, pets)
• Family history/genetic
• Other employment

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Consider the biological plausibility of your
diagnosis.

• Does it fit in with what you know about the
  causation and nature of diseases?