TY - JOUR T1 - Against all odds? Improving the understanding of risk reporting JF - British Journal of General Practice JO - Br J Gen Pract SP - e220 LP - e223 DO - 10.3399/bjgp12X630223 VL - 62 IS - 596 AU - Christine A'Court AU - Richard Stevens AU - Carl Heneghan Y1 - 2012/03/01 UR - http://bjgp.org/content/62/596/e220.abstract N2 - GPs are increasingly called upon to make or guide patients with choices about medical interventions, but there is gathering evidence that clinicians' understanding of risk is poor and, correspondingly, that their ability to communicate risk is deficient.1 In this article we aim to improve health professionals' understanding of risk reporting and clarify common misunderstandings in interpreting risk, odds, relative risk (RR), and odds ratios (ORs).The risk of an event (or disease) happening is simply the number of times it occurs divided by the number of occasions on which it could potentially occur. It is usually expressed as a proportion or as a percentage. For example, to give the risk of breast cancer is to say that for every eight women, one will develop breast cancer, which is a lifetime risk of 1/8, or 0.13.2 We might also express this by saying 12% of women develop breast cancer.This lifetime risk is not the same as the prevalence of breast cancer, which is the total number of cases in a given population at a specific time. Prevalence is dependent on factors including survivability and associated comorbidity, and is closer to 2% in the UK.2Using simple frequency statements — such as ‘one in eight women will develop breast cancer’ — avoids a potential source of miscommunication with patients. Gigerenzer's work highlights this issue in the description of a psychiatrist who was in the habit of advising patients that, on taking fluoxetine, there was ‘a 30–50% chance of developing a sexual problem’.3 He learned that patients interpreted this as meaning they would encounter difficulties during half their sexual encounters. He had intended to communicate that of every 10 people taking fluoxetine, three to five of them would experience difficulties. This exemplifies an important principle: physicians tend to … ER -