a study of primary care physicians in Massachusetts, 93 percent agreed that conveying risk numerically is important, and 63 percent felt that quantitative and qualitative communications are equally important, but only 36 percent felt that they could convey numerical risk information effectively (Gramling et al. 2004). One of the most difficult challenges in risk communication is conveying probabilistic information. The difficulty stems in part from the fact that most patients are interested in what their own chances of benefit and risk are, not population-level probabilities.

If physicians are not confident in their ability to communicate risks numerically, what can be done to help them? More generally, how can risk information about medication be communicated effectively? The magnitude of this challenge is evidenced by the fact that even after several decades of effort and a large body of evidence, there is still a lack of consensus concerning the most appropriate method by which to communicate medical risk.

Both individual-level (information directed toward the individual patient) and population-level (information about the population of which the individual is a member) risk information can be communicated in any of several formats—numerically, verbally, visually, or through the use of narrative. Numerical formats for presenting risk include percentages (e.g., 10 percent greater risk), frequencies (e.g., 1 out of 10 people is expected to have side effects), classical probabilities (e.g., 0.10 chance), and “numbers needed to treat” (e.g., need to treat 100 people to get one person to benefit). The advantages to using numbers include the following: they are precise, they add an aura of “scientific credibility,” they are easy to compare and convert to varying metrics, they can be used in existing or new algorithms, and they are verifiable. Numerical usage also has disadvantages, such as the discrepancy between actual (or objective) and perceived risks that results when numerical risk information is used, even just moments after the information has been provided. Dr. Lipkus stated that studies have shown that innumeracy is problematic across all educational levels, even among the college educated.

The problem of innumeracy raises the question, Why can’t we just verbally communicate the risk? Verbal terms tap into gut-level reactions, they seem to be easy, and they convey uncertainty on multiple levels. Yet verbal communication is vague, terminology is difficult to standardize across contexts and between people, and interpretation is highly variable.

If not verbal, how about visual communication? Visual aids can range from bar charts and line graphs to risk ladders and stick figures. The advantages of visual displays are that they can summarize lots of data; help the patient see patterns that would otherwise go undetected; help the patient perform some mathematical operations, such as comparisons,

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