BackgroundVarious types of framing can influence risk perceptions, which may have an impact on treatment decisions and adherence. One way of framing is the use of verbal terms in communicating the probabilities of treatment effects. We systematically reviewed the comparative effects of words versus numbers in communicating the probability of adverse effects to consumers in written health information.MethodsNine electronic databases were searched up to November 2012. Teams of two reviewers independently assessed studies. Inclusion criteria: randomised controlled trials; verbal versus numerical presentation; context: written consumer health information.ResultsTen trials were included. Participants perceived probabilities presented in verbal terms as higher than in numeric terms: commonly used verbal descriptors systematically led to an overestimation of the absolute risk of adverse effects (Range of means: 3% - 54%). Numbers also led to an overestimation of probabilities, but the overestimation was smaller (2% – 20%). The difference in means ranged from 3.8% to 45.9%, with all but one comparison showing significant results. Use of numbers increased satisfaction with the information (MD: 0.48 [CI: 0.32 to 0.63], p < 0.00001, I2 = 0%) and likelihood of medication use (MD for very common side effects: 1.45 [CI: 0.78 to 2.11], p = 0.0001, I2 = 68%; MD for common side effects: 0.90 [CI: 0.61 to 1.19], p < 0.00001, I2 = 1%; MD for rare side effects: 0.39 [0.02 to 0.76], p = 0.04, I2 = not applicable). Outcomes were measured on a 6-point Likert scale, suggesting small to moderate effects.ConclusionsVerbal descriptors including “common”, “uncommon” and “rare” lead to an overestimation of the probability of adverse effects compared to numerical information, if used as previously suggested by the European Commission. Numbers result in more accurate estimates and increase satisfaction and likelihood of medication use. Our review suggests that providers of consumer health information should quantify treatment effects numerically. Future research should focus on the impact of personal and contextual factors, use representative samples or be conducted in real life settings, measure behavioral outcomes and address whether benefit information can be described verbally.

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Background Uncertainty is integral to evidence-informed decision making and is of particular importance for preference-sensitive decisions. Communicating uncertainty to patients and the public has long been identified as a goal in the informed and shared decision-making movement. Despite this, there is little quantitative research on how uncertainty in health information is perceived by readers. Objective The aim of this study was to examine the impact of different uncertainty descriptions regarding the evidence for a treatment effect in a written research summary for the public. Methods We developed 8 versions of a research summary on a fictitious drug for tinnitus with varying degrees (Q1), sources (Q2), and magnitudes of uncertainty (Q3). We recruited 2099 members of the German public from a web-based research panel. Of these, 1727 fulfilled the inclusion criteria and were randomly presented with one of these research summaries. Randomization was conducted by using a centralized computer with a random number generator. Web-based recruitment and data collection were fully automated. Participants were not aware of the purpose of the study and alternative presentations. We measured the following outcomes: perception of the treatment effectiveness (primary), certainty in the judgement of treatment effectiveness, perception of the body of evidence, text quality, and intended decision. The outcomes were self-assessed. Results For the primary outcome, we did not find a global effect for Q1 and Q2 (P=.25 and P=.73), but we found a global effect for Q3 (P=.048). Pairwise comparisons showed a weaker perception of treatment effectiveness for the research summary with 3 sources of uncertainty compared to the version with 2 sources of uncertainty (P=.04). Specifically, the proportion of the participants in the group with 3 sources of uncertainty that perceived the drug as possibly beneficial was 9% lower than that of the participants in the group with 2 sources of uncertainty (92/195, 47.2% vs 111/197, 56.3%, respectively). The proportion of the participants in the group with 3 sources of uncertainty that considered the drug to be of unclear benefit was 8% higher than that of the participants in the group with 2 sources of uncertainty (72/195, 36.9% vs 57/197, 28.9%, respectively). However, there was no significant difference compared to the version with 1 source of uncertainty (P=.31). We did not find any meaningful differences between the research summaries for the secondary outcomes. Conclusions Communicating even a large magnitude of uncertainty for a treatment effect had little impact on the perceived effectiveness. Efforts to improve public understanding of research are needed to improve the understanding of evidence-based health information. Trial Registration German Clinical Trials Register DRKS00015911, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00015911 International Registered Report Identifier (IRRID) RR2-10.2196/13425

Background Uncertainty is integral to evidence-informed decision making and is of particular importance for preference-sensitive decisions. Communicating uncertainty to patients and the public has long been identified as a goal in the informed and shared decision-making movement. Despite this, there is little quantitative research on how uncertainty in health information is perceived by readers. Objective The objective of this study is to design an experiment to examine how different degrees of uncertainty (Q1) and different types of uncertainty (Q2) impact patients’ perception of treatment effectiveness, the body of evidence, text quality, and hypothetical treatment intention. The experiment also examines whether there is an additive effect when multiple sources of uncertainty are communicated (Q3). Methods We developed 8 variations of a research summary set in a hypothetical scenario for a treatment decision in the context of tinnitus. These were modified only in the degree of uncertainty relating to the evidence of the presented treatment. We recruited members of the German public from a Web-based research panel and randomized them to one of 8 variations of the research summary to examine the 3 research questions. The trial was only open to the members of the research panel. The outcomes are perception of the effectiveness of the treatment (primary), certainty in the judgement of treatment effectiveness, perception of the body of evidence relating to the treatment, text quality, and decisional intention (secondary). Outcomes were self-assessed. We aimed to recruit 1500 participants to the trial. The recruitment and data collection was fully automated. Ethical approval was waivered by an ethics committee because of the negligible risk to participants. Results This protocol is retrospectively published in its original format. In the meantime, the trial was set up and the data collection was completed. Data collection was conducted in May 2018. A total of 1727 eligible panel members were enrolled. Conclusions We aim to publish the results in a peer-reviewed journal by the end of 2019. In addition, results will be presented at conferences and disseminated among developers of guidance for the development of evidence-based health information and decision aids. Trial Registration German Clinical Trials Register DRKS00015911; https://www.drks.de/drks_web/navigate.do? navigationId=trial.HTML&TRIAL_ID=DRKS00015911 (Archived by WebCite at http://www.webcitation.org/77zyZTGzk) International Registered Report Identifier (IRRID) DERR1-10.2196/13425