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Knapp, P, Gardner, P, Carrigan, N et al.E Perceived risk of adverse drug reactions by patients using verbal descriptors, percentages and natural frequencies. Br J Health Psychol 2009; 14: 579-594

The British Journal of Health Psychology features research from two experiments involving users of the Cancer Research UK patient information website that examined the effectiveness of presenting adverse drug reaction risk information in the following forms:

• A form of `natural frequency'
• Percentages
• Verbal descriptors

In Experiment 1, 148 participants were asked to imagine that they had to take paclitaxel and were asked to estimate the risks of two side-effects occurring. In Experiment 2, 137 participants estimated the risk for three different side-effects occurring with ibuprofen. In both experiments, verbal descriptions (e.g. "uncommon" or "common"), for example led to higher estimates of risk compared to the other two formats. There was some evidence that people given information as frequencies (e.g. 1 in 10 people) were more accurate in their estimates than those given percentage information.

The researchers conclude that "these findings provide partial support for the advantages of a form of `natural frequencies' when presenting side-effects to patients. They also add weight to the growing body of research highlighting the deficiencies in using verbal descriptions of side-effect risk alone." The study author said "giving information about medication in a confusing way could be dangerous"¦.we need to explain risk in a way patients can relate to"¦for most people it is better to say 'three in 10 people will have side effects' rather than 30%."

Taken from National electronic Library for Medicines

www.nelm.nhs.uk/en/NeLM-Area/News/2009---August/13/Perceived-risk-of-adverse-drug-reactions-by-patients-using-verbal-descriptors-percentages-and-natural-frequencies-/