Background: It is important that patients are well-informed about risks and benefits of therapies to help them decide whether to accept medical therapy. Different numerical formats can be used in risk communication but It remains unclear how the different formats affect decisions made by real-life patients.
Aim: To compare the impact of using Prolongation Of Life (POL) and Absolute Risk Reduction (ARR) information formats to express effectiveness of cholesterol-lowering therapy on patients' redemptions of statin prescriptions, and on patients' confidence in their decision and satisfaction with the risk communication.
Design and setting: Cluster-randomised clinical trial in general practices. Thirty-four Danish GPs from 23 practices participated in a primary care-based clinical trial concerning use of quantitative effectiveness formats for risk communication in health prevention consultations.
Method: GPs were cluster-randomised (treating practices as clusters) to inform patients about cardiovascular mortality risk and the effectiveness of statin treatment using either POL or ARR formats. Patients' redemptions of statin prescriptions were obtained from a regional prescription database. The COMRADE questionnaire was used to measure patients' confidence in their decision and satisfaction with the risk communication.
Results: Of the 240 patients included for analyses, 112 were allocated to POL information and 128 to ARR. Patients redeeming a statin prescription totalled six (5.4%) when informed using POL, and 32 (25.0%) when using ARR. The level of confidence in decision and satisfaction with risk communication did not differ between the risk formats.
Conclusion: Patients redeemed statin prescriptions less often when their GP communicated treatment effectiveness using POL compared with ARR.
Trial registration: ClinicalTrials.gov NCT01414751.
Keywords: cardiovascular disease; decision making; general practice; patient participation; risk assessment; risk communication.