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Evaluating a combined (frequency and percentage) risk expression to communicate information on medicine side effects
Peter Knapp1, Peter Gardner, Brian McMillan
1Department of Health Sciences, University of York, York, UK. peter.knapp@york.ac.uk
Objectives:
The study evaluated the interpretation of, and preferences for, numerical information on side-effect incidence when presented in three different formats.
Methods:
It used a controlled design, with participants allocated at random to receive one of the three formats. Participants were recruited via a pop-up window on the CancerHelp UK website. The sample comprised 129 website users, of whom 96% were women and 86% had cancer, who received frequency information on four side effects of tamoxifen, using one of three risk expressions (percentages, e.g. 'affects 25% of people'; frequencies, e.g. 'affects 1 in 4 people'; combined, e.g. 'affects 1 in 4 people (25%)'). They then interpreted information on tamoxifen and its effect on health, and estimates of side-effect frequency, and then stated a preference from the three risk expression formats.
Key Findings:
The results showed that the three formats did not influence participants' ratings of the information or their side-effect estimates. However, more than half (53%) the participants preferred the combined (frequency and percentage) format. In conclusion, a combined risk expression format performed no worse than percentages or frequencies alone and was preferred by a majority.
Conclusions:
The three risk expression formats did not differ in their effect on participants' interpretations. However, the preferred format was the combined (frequency and percentage) risk expression.
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