Background/Purpose: Doctors and patients make treatment decisions after weighing benefits and harms. For harms, while people prefer treatments with smaller risks, how they react to ambiguity—i.e., uncertainty arising from limitations in the reliability, credibility, or adequacy of risk information (often presented as a range of risks) – is less well understood. The objective of this study was to determine the relative importance of the magnitude of risk and ambiguity in the treatment decision-making context.

Methods: We invited members of an online panel to complete a survey which sought choices between two hypothetical rheumatoid arthritis treatments based on different levels of 4 attributes: probability of benefit (40%,55%,70%), probability (risk) of iatrogenic harm requiring treatment withdrawal (10%,20%,30%), ambiguity regarding risk of harm, expressed by risk estimate imprecision (none: point-estimate, low: range+/-5%, high: range+/-10%), and life expectancy (8,9,10 years). Each respondent answered 10 pairwise Discrete Choice Experiment questions indicating strength of preference for each treatment, described using differing levels for each attribute as generated by a D-efficient experimental design. Conditional and mixed logit models were used to estimate coefficients for each attribute level and allow for estimation of marginal willingness to pay (WTP), in this case the duration of life they would be willing to give up to move between each of the attribute levels in the survey.

Results: Of 252 respondents, the mean age was 34 (range 20-67), 68% were male, and 52% had an education level of high school or less. Respondents placed greatest value on greater probability of benefit (WTP=1.34 years for 70% vs 40%, p<0.001), with lower but significant values for lower risk of harm (WTP=0.4 years for 10% vs 30%, p<0.001), and lower ambiguity (WTP=0.14 years, none vs high, p<0.001). Preliminary investigation of interactions suggested respondents were ambiguity-seeking when the risk of harm was low (10%), ambiguity-averse when the risk was high (30%), and ambiguity-neutral at the intermediate risk (20%).  The degree of ambiguity aversion at high risk (30%) increased with the degree of imprecision in the risk estimate.

Conclusion: Current rheumatology patient information sources present harms of treatments by either providing point estimates (e.g. 3%, and ignore the ambiguity) or by providing ranges of risk estimates (e.g. 2-5%). This study suggests that providing ranges to communicate ambiguity make treatments more appealing when risks are small, but less appealing when risks are larger. While more research is needed to quantify differences in responses to ambiguity at other levels of risk, and for other outcomes, treatments, and disease states, this study highlights the implications of how risks are described, and the importance of developing strategies to communicate ambiguity in risk information.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/influence-on-treatment-decision-making-of-providing-numerical-ranges-of-side-effect-risks/