Primer: Demystifying risk--understanding and communicating medical risks.

Assessments of risk are a critical part of the practice of evidence-based medicine. Comprehension of various risk measures, such as absolute risk, relative risk, attributable risk, odds ratio, and hazard ratio, is essential to understand the medical literature, and to communicate health risks effectively. Complex risk measures, including number needed to treat and survival estimates that are adjusted for competing risks, are often misunderstood. Communication of these concepts to patients can be a challenge. The patient's perception of risk stems not only from the way risks are stated, but also from family history, personal experiences, cultural norms, and beliefs. A multifaceted approach to risk communication that uses both qualitative and quantitative assessments of risk, and addresses the timing and permanence of risks, is necessary to ensure the patient understands the potential risks. Successful communication involves interaction with the patient to understand the patient's perspective and to aid in personalized decision-making. In the face of uncertainty, making a provisional decision with a plan to review it later can be a good strategy. Verifying the patient's comprehension can help ensure that the decisions reached are informed and acceptable.