Evaluating a combined (frequency and percentage) risk expression to communicate information on medicine side effects to patients

Peter Knapp, Peter Gardner, Brian Mcmillan, David K Raynor, Elizabeth Woolf

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Pages (from-to)226-32
Number of pages7
JournalThe International journal of pharmacy practice
Issue number4
Publication statusPublished - Aug 2013


  • Adolescent
  • Adult
  • Aged
  • Antineoplastic Agents, Hormonal
  • Communication
  • Female
  • Humans
  • Internet
  • Male
  • Middle Aged
  • Neoplasms
  • Patient Education as Topic
  • Patient Preference
  • Risk
  • Tamoxifen
  • Young Adult
  • Journal Article
  • Randomized Controlled Trial


Dive into the research topics of 'Evaluating a combined (frequency and percentage) risk expression to communicate information on medicine side effects to patients'. Together they form a unique fingerprint.

Cite this