Using an Using an occupational historyoccupational history

Grant McMillanGrant McMillan

Hon Senior Clinical LecturerHon Senior Clinical Lecturer

Institute of Occupational and Environmental Health University of Birmingham

Number 5 of a series of lectures and tutorials for medical undergraduates

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.

Categories of work-related diseasesCategories 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

Criteria for diagnosing an Criteria for diagnosing an occupational/work-related diseaseoccupational/work-related disease

• Effect

• Exposure

• Time sequence

• Competing causes

• Biological plausibility

Each of these is now considered in turn

EffectEffect

• 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?

ExposureExposure

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?

ExposureExposure

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.

Time sequenceTime sequence

• Exposure must be prior to onset of illness.Exposure must be prior to onset of illness.

• Immediate effects eg hydrogen cyanideImmediate effects eg hydrogen cyanide

• Hours delay of effects eg phosgene, Hours delay of effects eg phosgene, oxides of nitrogen, arc eye.oxides of nitrogen, arc eye.

• Weeks or months delay of effects – Weeks or months delay of effects – dermatitis, asthmadermatitis, asthma

• For cancers - appropriate latency periodFor cancers - appropriate latency period

Consider non-occupational causesConsider non-occupational causes

• What is differential diagnosis?

• Non-occupational causes

• Environmental

• Social (smoking, alcohol, hobbies, pets)

• Family history/genetic

• Other employment

Consider the biological Consider the biological plausibility of your diagnosis. plausibility of your diagnosis.

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