The influence of treatment effect size on willingness to adopt a therapy.

Background: Physicians are slow to adopt novel therapies, and the reasons for this are poorly understood. The authors sought to determine if the size of the treatment effect of a novel therapy influences willingness to adopt it.

Methods: We developed 2 experimental vignette pairs describing a trial of a therapy for a hypothetical disease that showed a statistically significant mortality benefit. The size of the mortality effect was varied in vignettes of a pair (3% v. 10%). The 2 experimental vignette pairs differed in whether study enrollment was reported. Vignettes were mailed to a random sample of physicians using an intersubject design. The main study outcome was respondents' willingness to adopt the hypothetical therapy, based on the results of the hypothetical trial.

Results: There were 124 and 89 respondents to vignette pairs 1 and 2, respectively. In vignette pair 1, 91% versus 71% of respondents adopted the therapy when it reduced mortality by 10% and 3%, respectively (P = 0.0058). For vignette pair 2, 88% versus 51% of respondents adopted the therapy when it reduced mortality by 10% and 3%, respectively (P = 0.0002). In both vignette pairs, nonadopters were more likely than adopters to report side effects of the therapy as a principal reason for their decision.

Conclusions: In this study, respondents were less likely to adopt a lifesaving therapy if its associated mortality reduction was 3% compared to 10%. Because most therapies for major medical conditions reduce mortality within or below this range, and because there were no opportunity costs associated with the adoption of the therapy, we believe that this effect represents a bias. Further investigation will be required to determine its prevalence and mechanism.