Objectives: To assess the influence of the form of presentation of the results of clinical trials on the quantitative perceptions of cardiologists regarding the efficacy of drugs for the primary and secondary prevention of coronary heart disease and their likelihood of prescribing them.
Method: We conducted a survey of 1,408 cardiologists in Spain who were randomly allocated of three questionnaires that used different measurements to evaluate the impact of published clinical trials.
Results: Five-hundred and fifty-nine questionnaires (40%) were suitable for analysis. On a scale of 0 to 10, the following mean efficacy estimates were obtained from questionnaire items that focused, respectively, on the results of clinical trials in terms of relative risk reduction, absolute risk reduction, and number needed to treat: primary prevention with statins: 6.79, 6.38 and 5.43; primary prevention with aspirin: 6.84, 5.06 and 4.25; secondary prevention with statins: 8.16, 7.76 and 7.54; secondary prevention with ACE inhibitors: 7.11, 7.81 and 7.19, and secondary prevention with beta-blockers: 7.22, 7.43 and 6.98. The likelihood that a drug treatment would be prescribed was not influenced very much by the form of presentation of the trial results.
Conclusions: Presenting the results of clinical trials in the form of relative risk reduction, as compared with presenting results in terms of absolute risk reduction or number needed to treat, led to overestimation of the efficacy of interventions without influencing the likelihood of prescribing a given drug therapy.