Introduction: Not much is known about how Singaporeans perceive and react to risk presentation. There is no consensus on whether the European Union guidelines for describing the risk of side effects are valid. This study investigated the effect of different modes of risk presentation on how Singaporeans perceive and react to medical risk. Furthermore, we investigated the practical usage of qualitative phrases, the European Union’s adjectives in particular, in describing levels of risk. Materials and Methods: A hypothetical situation about the risk of side effects of an influenza vaccine was presented in either a probability format (i.e., 5%; n = 42) or a frequency format (i.e., 1 out of 20; n = 43). The 2 versions of questionnaire were handed out in an alternate order to a convenience sample of 47 healthcare professionals and 38 university students. Results: Respondents presented with a “5% risk” were more likely to describe the risk as “uncommon” or “rare”, as compared to respondents presented with a risk of “one out of twenty” (P <0.01). Furthermore, the former showed more willingness to accept the influenza vaccine described in the hypothetical situation than in the latter, but this was not statistically different (67% versus 54%; P >0.1). Conclusions: Modes of risk presentation affect how people perceive risk, even among people who are highly educated.
The communication of risk is an important aspect of healthcare and medical research. In 2003, the British Medical Journal1 and the Journal of the Royal Statistical Society2 each published a special issue on this topic, highlighting its relevance to both clinicians and statisticians. There are various ways of presenting the same level of risk. For instance, one may say, “Patients similar to Mr Jones are estimated to have a 10% probability of committing an act of violence to others during the first several months after discharge from a psychiatric facility.” But the same risk may also be expressed as “1 out of 10 patients” or “10 out of 100 patients”.3 In the context of describing the side effect of a drug, a 10% risk may be described as “common”.4 In a study of 479 members of the American Psychology-Law Society, almost all of whom had experience in clinical or forensic practice, the respondents were given information presented in different ways about the risk of a mental health patient committing a violent act after being discharged.1 They were then asked to make judgements about the patient’s suitability for discharge from the hospital. About 11% of the respondents who were presented with a “10% probability” did not recommend discharge of the patient. In contrast, 21% of the respondents who were presented with a risk of “10 out of 100” did not recommend discharge of the patient. It has been suggested that when a risk is presented in a probability format (e.g., 5%), people may be unable to appreciate the actual risk and may tend to underestimate it. Hence, presentations using the frequency format (e.g., 1 out of 20) or in terms of words (e.g., probable) are sometimes suggested.3,5,6
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