Patients may overestimate risk of side-effects from qualitative drug information

Authors of a research letter in this week’s issue of THE LANCET are calling for EU guidelines to be reviewed after results of research which shows that patients only given qualitative information about the side-effects of drugs substantially overestimate their personal risk.

To make informed decisions about taking medicinal drugs, people need accurate information about side-effects. An EU guideline now recommends the use of qualitative descriptions for five bands of risk, ranging from very rare (affecting In the largest of four studies, the investigators assessed 360 adults who were either given qualitative descriptions of drug side-effects (‘common’ and ‘rare’), or corresponding quantitative descriptions (2% and 0.02%). Participants given the term common rated their personal risk of having a side-effect as 50%, whereas those given the equivalent numerical value of 2% rated their risk as 9.5%; people who were told their chance of side-effects were rare estimated their risk as 21%, compared with 7% for patients who were given a quantitative risk of 0.02%.

Dianne Berry comments: “If people are unable to estimate the risk of occurrence of side-effects, they cannot be expected to make informed decisions about medicinal drug taking. Our results strongly suggest that the qualitative descriptions recommended by the EU lead to gross overestimation of risk, with results from all four studies showing a similar level of overestimation.”

Contact: Professor Dianne Berry, Department of Psychology, University of Reading, Earley Gate, Whiteknights, Reading, RG6 6AL, UK; T) +44 (0) 118 931 8526; F) +44 (0) 118 931 6715; E) D.C.Berry@Reading.ac.uk

Professor D.K.Raynor, School of Healthcare Sciences, University of Leeds, Leeds, LS2 9JT, UK; T) +44 (0)113 233 1251; F) +44 (0)113 233 1284; E) D.K.Raynor@leeds.ac.uk