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08-01-2012 | Stroke | Article

Data presentation may bias treatment choices for asymptomatic carotid stenosis


Free abstract

MedWire News: The terms in which the potential benefits of carotid revascularization are framed can sway patients toward surgery rather than intensive medical therapy, shows a randomized trial.

The findings show that presenting data in relative terms risks biasing patients toward treatments that may actually only be of minimal benefit.

The trial included 409 patients attending a neurology clinic for reasons not related to carotid stenosis. They were randomly assigned to view one of five 30-second videos in which a physician presenter outlined the risks and benefits of carotid surgery versus medical therapy for asymptomatic carotid stenosis (ACS).

After viewing the video, the participants completed a survey including a treatment choice, with 48.4% opting for surgery.

Younger participants (<55 years) and those with more than a high school education tended to favor surgery over medical therapy, but these associations were not statistically significant. The participants' gender and race did not affect their decisions, and neither did the race or gender of the physician presenter (Black or White, man or woman).

The only factor significantly associated with the participants' treatment decisions was the format in which the data were presented, Brian Silver (Rhode Island Hospital, Providence, USA) and team report in the journal Neurology.

Specifically, participants were 3.3 times more likely to opt for surgery over medical therapy if they viewed a video giving stroke risk as a relative risk at 5 years, rather than an annualized absolute risk, and 3.1 times more likely if given a qualitative assessment of surgical benefits. These increases equated to a 20-30% absolute increase in the likelihood of opting for surgery.

Participants were no more likely to choose surgery over medical therapy if presented with an absolute stroke risk at 5 years or absolute disease-free survival at 5 years, relative to annualized absolute stroke risk.

The effect of data framing was most prominent among participants younger than 55 years, who were more than four times more likely to choose surgery over medical therapy if presented with relative stroke risk or a qualitative assessment rather than an annualized absolute risk. Among older patients, the effect remained significant for the qualitative assessment but not the relative risk presentation.

The impact of presenting data qualitatively or as a relative risk was also magnified among participants who had more than a high school education.

Editorialists Gustavo Saposnik (University of Toronto, Canada) and Raffi Topakian (Academic Teaching Hospital Wagner-Jauregg Linz, Austria) compare the effects to those of marketing, saying that "patients tend to take risk when presented with immediate 'bigger savings' in relative terms compared to absolute discounts."

They caution that the benefits of surgery presented to patients in the trial were "fairly optimistic," given that carotid revascularization has not been formally tested against modern intensive medical therapy.

"Nevertheless, the present study provides novel information in the understanding of patients' preferences and choices in ACS," say Saposnik and Topakian.

"The management of patients with ACS continues to polarize opinion, as up to 94% of interventions may not benefit the patient. In this setting, inadequate information framing may bias ACS patients toward unnecessary carotid revascularization."

MedWire ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2012

By Eleanor McDermid