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

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 diseases IWork 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 occupational/work-related disease Effect Exposure Time sequence Competing causes Biological plausibility Each of these is now considered in turn

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?

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?

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.

Time 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, oxides of nitrogen, arc eye.Hours delay of effects eg phosgene, oxides of nitrogen, arc eye. Weeks or months delay of effects – dermatitis, asthmaWeeks or months delay of effects – dermatitis, asthma For cancers - appropriate latency periodFor cancers - appropriate latency period

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

Consider the biological plausibility of your diagnosis. Does it fit in with what you know about the causation and nature of diseases?