Acoustic-based rule out of stable coronary artery disease: the FILTER-SCAD trial

Abstract Background and aims Overtesting of low-risk patients with suspect chronic coronary syndrome (CCS) is widespread. The acoustic-based coronary artery disease (CAD) score has superior rule-out capabilities when added to pre-test probability (PTP). FILTER-SCAD tested whether providing a CAD score and PTP to cardiologists was superior to PTP alone in limiting testing. Methods At six Danish and Swedish outpatient clinics, patients with suspected new-onset CCS were randomised to either standard diagnostic examination (SDE) with PTP, or SDE plus CAD score, and cardiologists provided with corresponding recommended diagnostic flowcharts. The primary endpoint was cumulative number of diagnostic tests at one year and key safety endpoint major adverse cardiac events (MACE). Results In total 2008 patients (46% male, median age 63 years) were randomised from October 2019 to September 2022. When randomised to CAD score (n=1002), it was successfully measured in 94.5%. Overall, 13.5% had PTP ≤5%, and 39.5% had CAD score ≤20. Testing was deferred in 22% with no differences in diagnostic tests between groups (p for superiority =0.56). In the PTP ≤5% subgroup, the proportion with deferred testing increased from 28% to 52% (p<0.001). Overall MACE was 2.4 per 100 person-years. Non-inferiority regarding safety was established, absolute risk difference 0.4% (95% CI -1.85 to 1.06) (p for non-inferiority = 0.005). No differences were seen in angina-related health status or quality of life. Conclusions The implementation strategy of providing cardiologists with a CAD score alongside SDE did not reduce testing overall but indicated a possible role in patients with low CCS likelihood. Further strategies are warranted to address resistance to modifying diagnostic pathways in this patient population.