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A RASH TO JUDGEMENT?

Heldane had been on the market for barely a year when numerous anecdotal reports began to appear suggesting that the drug produced lichenoid eruptions.

Marysia, a young clinician, at the Huronsville Clinic, obtained the following information from hospital records:

In a six month period, the eruptions have been observed in 6 out of 23 patients prescribed the drug. Similar rashes have been seen in 4 out of 50 patients who have not been known to take the drug. Marysia estimates the odds-ratio as 4.05. When she shows the data to Dr. Mammon, the Head of the Unit, he suggests that she contact the manufacturers of the drug.

Presented with the information, the manufacturers are concerned and offer to fund a larger cohort study to gather more evidence. After a year's intensive study the following data are obtained:

	Rash	No Rash
Drug Exposure	23	75
No Drug Exposure	16	91

This leads to an attributable risk due to the drug of 0.08. Although the manufacturers appear satisfied, Marysia is left wondering as to why she obtained such high odds-ratios in the first instance.

Comments:

This was the first problem used in the course. It provided an opportunity for students to explore epidemiological terms, consider appropriate study-designs and introduced them to the analysis of adverse drug reactions, which forms the basis of many studies in pharmacoepidemiology. The problem is a straightforward presentation of a limited set of data.