The theory of planned behaviour in a randomized trial of a decision aid on cardiovascular risk prevention

Krones, Tanja; Keller, Heidemarie; Becker, Annette; Sönnichsen, Andreas; Baum, Erika; Donner-Banzhoff, Norbert

doi:10.1016/j.pec.2009.06.010

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Volume 78, Issue 2 , Pages 169-176, February 2010

The theory of planned behaviour in a randomized trial of a decision aid on cardiovascular risk prevention

Tanja Krones
- Department of Family Practice, University of Marburg, Germany & Bioethics-Clinical Ethics, University of Marburg, Baldingerstrasse, 35033 Marburg, Germany
- Corresponding author. Tel.: +49 6421 5866487; fax: +49 6421 5866585.
Heidemarie Keller
- Department of Family Practice, University of Marburg, Germany & Bioethics-Clinical Ethics, University of Marburg, Baldingerstrasse, 35033 Marburg, Germany
Annette Becker
- Department of Family Practice, University of Marburg, Germany & Bioethics-Clinical Ethics, University of Marburg, Baldingerstrasse, 35033 Marburg, Germany
Andreas Sönnichsen
- Department of Family Practice, University of Salzburg, Austria
Erika Baum
- Department of Family Practice, University of Marburg, Germany & Bioethics-Clinical Ethics, University of Marburg, Baldingerstrasse, 35033 Marburg, Germany
Norbert Donner-Banzhoff
- Department of Family Practice, University of Marburg, Germany & Bioethics-Clinical Ethics, University of Marburg, Baldingerstrasse, 35033 Marburg, Germany

Received 23 September 2008; received in revised form 29 June 2009; accepted 29 June 2009. published online 10 August 2009.

Abstract

Objective

To assess the feasibility and outcome of measuring the theory of planned behaviour (TPB) in patients receiving routine counselling versus counselling with a decision aid (DA) during primary care consultation on cardiovascular risk prevention.

Methods

A DA was developed, based on models of shared decision-making (SDM) and the TPB. We evaluated the impact of the intervention in a randomized controlled trial. Main outcomes were previously reported. To assess the intermediate social cognitive processes and our theoretical framework, we evaluated the impact of the intervention on a TPB scale.

Results

The TPB scale showed satisfactory measurement properties. Factor analysis (main component analysis, confirmatory model) could mostly replicate the assumptions of the model. 44% of variance of the behavioural intention to adhere to the decision after counselling was explained in linear regression models. Of the TPB components, only attitude towards the decision and moral norm were significantly more positive in the intervention. No difference was found with regard to intention to adhere to the decision. High risk resulted in higher values of the TPB components in both groups.

Conclusion

Most DAs are developed and tested without explicitly referring to a theoretical model of psychosocial processes. The TPB may serve as a useful theoretical framework.

Practice Implications

Trials on DAs demonstrate positive effects on psychological outcomes of patients without leading to better objective health results. Our study might contribute to an explanation: DAs might not cause stronger adherence to decisions even though one's attitude towards the decision becomes more positive.

Keywords: Decision aids, Shared decision-making, Decision support, Theory of planned behaviour, Cardiovascular diseases, Risk, Primary health care