Background Studies have found that patients ignore probabilities when making treatment decisions.
Objectives The objective of this study was to examine whether addition of an icon array (IA), a series of three consecutive balance-beam (BB) illustrations depicting how medications regulate the immune system, or both resulted in patients being able to better differentiate between an uncommon (2%) and rare (0.2%) adverse event (AE).
Methods Patients currently being treated for a chronic inflammatory rheumatic disease were mailed a survey in which they were asked to imagine that their symptoms had recently worsened and that their physician was recommending a new medication. The medication was described using eight scenarios (manipulated using a 2x4 design). We varied the probability of a serious AE (pneumonia requiring hospitalization): 2% vs 0.2% and the risk presentation format: numbers only, numbers + IA, numbers + BB, and numbers + IA + BB. Route of administration, benefit, and cost were held constant. Each subject responded to a single, randomly-assigned scenario. Dependent variables included perceived riskiness, worry, global gist related to the acceptability of the AE, and willingness to take the medication (all measured on 5-point ordinal scales). We hypothesized that the IA and BB formats would result in 1) lower perceived riskiness and worry, and 2) greater acceptability of the AE and willingness to take the medication in the 0.2% vs 2% scenarios. Socioeconomic status (SES) was defined based on difficulty paying for medication and education level.
Results We mailed 1453 surveys. 465 patients completed and mailed the survey back (32% response rate). Overall, the mean age of responders was 58.99 (SD=14.85); 79.7% of were female; 83.2% White and 39.1% had a low SES. There were no statistical differences in demographic or clinical characteristics across the four risk presentation formats. Mean (SD) perceived riskiness, worry, global gist, and willingness to take the medication for 2% versus 0.2% chance of the AE, by SES level, are presented in the Image.
Perceived riskiness was lower for a 0.2% versus 2% risk of the AE in the numbers + IA condition in higher SES subjects. Lower SES subjects who viewed both IA and BB were more worried about the AE and found the AE to be less acceptable in the 0.2% versus 2% condition.
Conclusions With the exception of the IA's impact on perceived riskiness among subjects with higher SES, the risk formats used did not enable subjects to correctly differentiate between a 0.2% and a 2% risk of a serious AE. These results highlight the lack of impact of quantitative risk information on patients' risk perceptions.
Disclosure of Interest None declared