Purpose: To evaluate the relationship between preferences for quantitative information in risk communication and objective measures of how well the quantitative information is understood.
Method: A cross sectional survey was conducted. Participants were randomly recruited from an adult primary care population. Clinical vignettes were developed to simulate a discussion between a patient and physician regarding the risks and benefits of breast and colorectal screening, respectively. The clinical vignettes presented risk information using both probability and frequency formats. After reading the vignettes, participants responded to multiple choice questions testing their understanding of the information presented. In a second exercise, participants took the Medical Data Interpretation Test (MDIT). This MDIT is a validated instrument that assesses that ability to critically interpret the results of medical studies as they may be presented to the lay public. Upon completion of the clinical vignette exercise and MDIT, respectively, participants were asked their perceptions of the usefulness of presenting such information with numbers. Univariate and multivariate analyses were done to evaluate the association of preferences for numeric information with an objective measure of how well the information was understood.
Results: There were 359 participants in the study; 70% were white and 27% were black. Twenty-eight percent (28%) had no more than a high school education. Eighty-six percent (86%) and 78% strongly agreed or agreed that the quantitative information related to cancer screening and medical studies respectively, was useful. Clinical vignette knowledge scores ranged from 0 to 9 (mean 6.2, SD 2.0). MDIT scores ranged from 1-18 (mean 9.5, SD 3.2). In univariate analysis, those that strongly agreed or agreed that quantitative information was helpful were no more likely to correctly interpret the clinical vignettes than those who were neutral or did not agree. However, MDIT scores were higher among those that strongly agreed or agreed that numbers were helpful in communicating information about medical studies (p=0.018). This association persisted after controlling for age, gender, race, education, and income (p=0.049).
Conclusion: In this study, the association of perceived usefulness with objective knowledge of the information presented was inconsistent and varied with context. These findings highlight the need to assess level of understanding of quantitative information irrespective of the subject perceptions of the patient regarding the desire for quantitative information.
Candidate for the Lee B. Lusted Student Prize Competition