The impact of the format of graphical presentation on health-related knowledge and treatment choices.

To evaluate the ability of six graph formats to impart knowledge about treatment risks/benefits to low and high numeracy individuals. Participants were randomized to receive numerical information about the risks and benefits of a hypothetical medical treatment in one of six graph formats. Each described the benefits of taking one of two drugs, as well as the risks of experiencing side effects. Main outcome variables were verbatim (specific numerical) and gist (general impression) knowledge. Participants were also asked to rate their perceptions of the graphical format and to choose a treatment. 2412 participants completed the survey. Viewing a pictograph was associated with adequate levels of both types of knowledge, especially for lower numeracy individuals. Viewing tables was associated with a higher likelihood of having adequate verbatim knowledge vs. other formats (p<0.001) but lower likelihood of having adequate gist knowledge (p<0.05). All formats were positively received, but pictograph was trusted by both high and low numeracy respondents. Verbatim and gist knowledge were significantly (p<0.01) associated with making a medically superior treatment choice. Pictographs are the best format for communicating probabilistic information to patients in shared decision making environments, particularly among lower numeracy individuals. Providers can consider using pictographs to communicate risk and benefit information to patients of different numeracy levels.