Cost-effectiveness of adding a non-invasive acoustic rule-out test in the evaluation of patients with symptoms suggestive of coronary artery disease: rationale and design of the prospective, randomised, controlled, parallel-group multicenter FILTER-SCAD trial

INTRODUCTION: Most patients with symptoms suggestive of chronic coronary syndrome (CCS) have no obstructive coronary artery disease (CAD) and better selection of patients to be referred for diagnostic tests is needed. The CAD-score is a non-invasive acoustic measure that, when added to pretest probability of CAD, has shown good rule-out capabilities. We aimed to test whether implementation of CAD-score in clinical practice reduces the use of diagnostic tests without increasing major adverse cardiac events (MACE) rates in patients with suspected CCS. METHODS AND ANALYSIS: FILTER-SCAD is a randomised, controlled, multicenter trial aiming to include 2000 subjects aged ≥30 years without known CAD referred for outpatient assessment for symptoms suggestive of CCS. Subjects are randomised 1:1 to either the control group: standard diagnostic examination (SDE) according to the current guidelines, or the intervention group: SDE plus a CAD-score. The subjects are followed for 12 months for the primary endpoint of cumulative number of diagnostic tests and a safety endpoint (MACE). Angina symptoms, quality of life and risk factor modification will be assessed with questionnaires at baseline, 3 months and 12 months after randomisation. The study is powered to detect superiority in terms of a reduction of ≥15% in the primary endpoint between the two groups with a power of 80%, and non-inferiority on the secondary endpoint with a power of 90%. The significance level is 0.05. The non-inferiority margin is set to 1.5%. Randomisation began on October 2019. Follow-up is planned to be completed by December 2022. ETHICS AND DISSEMINATION: This study has been approved by the Danish Medical Agency (2019024326), Danish National Committee on Health Research Ethics (H-19012579) and Swedish Ethical Review Authority (Dnr 2019-04252). All patients participating in the study will sign an informed consent. All study results will be attempted to be published as soon as possible. TRIAL REGISTRATION NUMBER: NCT04121949; PRE-RESULTS.