The impact of the format of graphical presentation on health-related knowledge and treatment choices
Introduction
Improving informed medical decision making has been identified as a priority in the U.S. healthcare system [1], [2], [3]. Ensuring medical decisions are informed that patients have an accurate understanding of the risks and benefits associated with their treatment options [3], [4], [5]. Although such risk and benefit information are often presented numerically, research has shown that many Americans have difficulty in understanding and processing numbers [6], [7], [8]. The Adult Literacy and Lifeskills survey conducted in 2003 found that U.S. adults had lower numeracy scores than those from four other countries (Switzerland, Norway, Bermuda, and Canada) [9]. Moreover, even for those with high numeracy, the stress of a new diagnosis can make it difficult to process new and complex numerical information [10].
However, tools designed to improve informed medical decision making often fail to include visual aids, such as graphs or tables, to help convey complex risk and benefit information [11], [12]. Although inclusion of graphical information in decision aids is strongly recommended by the International Patient Decision Aids Standards Committee [13], there is little consensus regarding which methods for conveying information to patients are most likely to achieve the necessary level of understanding about treatment risks and benefits. There is also evidence that some formats in which numerical information is presented may bias patients and/or have unanticipated effects on their understanding of the information [12], [14].
The best method for presenting numerical information may differ based on the numeracy of the reader. A recent review article discussed the fact that different risk communication methods may be needed for individuals with low vs. high levels of numeracy [10]. Although there are some studies of how to present numerical information effectively [12], [15], [16], [17], [18], [19], [20] virtually none have had sufficient numbers of low and high numeracy subjects to evaluate whether formats may be more or less effective in these different groups [7], [10]. There is also a lack of research to describe how patients perceive different types of graphs (e.g., whether a particular type of graph is trustworthy or not) [15].
The main objective of this analysis was to evaluate the ability of six types of numerical communication formats (pie chart, bar graph, pictograph, modified pictograph or “sparkplug,” modified pie graph or “clock,” and table—see Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6 for examples), to impart knowledge about treatment risks/benefits in a hypothetical medical decision making scenario among low and high numeracy individuals. Secondary objectives were to assess participants’ perceptions of the graphs, and to assess with the association between knowledge and making the optimal treatment choice.
Section snippets
Methods
An online hypothetical medical decision making scenario was developed by our research team. Participants were randomized to view treatment risk and benefit information in one of the six numerical communication formats (from now on referred to as “graph formats”) and to answer a series of questions. Study participants were drawn from a panel of Internet users administered by Survey Sampling International (SSI) who voluntarily agreed to receive invitations to fill out questionnaires, as we have
Description of the sample
A total of 3153 participants logged onto the website and began the survey. Of these, 2412 participants (76.5%) answered all questions and were included in the analyses. The final sample was 52% women, 82% self-identified white, and had an average age of 49 years (range:18–90). Eighteen percent had a high school education or less, 44% had some college or trade school, and 38% held a bachelor's degree or more. Fifty percent of participants were classified as lower numeracy. Of note is the finding
Discussion
Our results are consistent with others who have shown that the presentation of risk and benefit information in different formats will have different effects on how viewers evaluate the information [12], [15], [16], [17]. Schapira et al. recently showed that patients perceived lifetime breast cancer risk to be lower when risk information was communicated with a bar graph compared with a pictorial display of risk (either using human forms or rectangular forms) [15]. Our results are also in line
Acknowledgements
Financial support for this study was provided by a grant from the National Institutes for Health (R01 CA87595). Dr. Zikmund-Fisher is supported by a career development award from the American Cancer Society (MRSG-06-130-01-CPPB), and Dr. Fagerlin is supported by an MREP early career award from the U.S. Department of Veterans Affairs.
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