Evaluation of the 2024 European Society of Cardiology risk-factor and calcium score-weighted clinical likelihoods as gatekeeper for patients with suspected chronic coronary syndrome referred for PET

Abstract Introduction Despite high clinical suspicion, most advanced cardiac tests for chronic coronary syndromes (CCS) are normal. Gatekeeper algorithms using the 2019 European Society of Cardiology (ESC) pre-test probability and Coronary Artery Calcium Score (CACS) can help to safely reduce unnecessary scans, radiation and costs. Purpose Study aim was to evaluate the diagnostic algorithm proposed by the ESC 2024 guidelines. Methods Three diagnostic algorithms (figure 1) based on the risk factor-weighted clinical likelihood (RF-CL) and CACS-CL (RF-CL + CACS) as described in the 2024 ESC CCS guidelines, were retrospectively applied to 1,792 consecutive patients with suspected CCS referred for 82Rb-Positron Emission Tomography (PET). Reduction of normal scan results, radiation exposure, and costs were compared with the current gold standard (CACS + PET in every patient). Endpoints were defined as small ischemia (SDS ≥2) and relevant ischemia (≥10% of myocardium). Results Mean age of the patients was 65±11 years; 43% were female. Median RF-CL and CACS-CL PTP were 11% 6, 19 and 12% 3, 28, respectively. As shown in figure 2, RF-CL and CACS-CL classified 22.0% and 34.5% to very low CL (≤5%), respectively. Algorithm 1 would have reduced radiation and costs by 22.0% with an acceptable gatekeeper performance. Algorithm 2 would have deferred the largest proportion of patients (36%) from testing but would have led to missed ischemia in 2.0%. Algorithm 3 had an optimal gatekeeper performance with a potential reduction of radiation and costs by 28.7% and 29.7% without compromising patient safety (sensitivity/NPV 93.2%/98.4% for small and 97.0%/99.7% for relevant ischemia). Conclusion Algorithm 3 showed the best overall gatekeeper performance. It significantly reduced the number of normal scan results, radiation exposure, and costs without significantly missing relevant ischemia suggesting favourable patient safety. Hence, introducing CACS for triage may help to optimally allocate limited healthcare resources while maintaining patient’s safety. Figure legends: Figure 1: The upper part depicts the three different diagnostic algorithms. Depending on the clinical likelihood, a PET scan would be performed or withheld. The pie chart diagrams indicate the number of patients and the proportion of abnormal findings in the corresponding group. The grey boxes indicate scan results which would not be available if the algorithm would have been used. Test characteristics refer to the detection of a small ischemia (SDS ≥2). CACS: coronary artery calcium score. RF-CL: risk factor-weighted clinical likelihood. CACS-CL: CACS and risk factor-weighted clinical likelihood. NPV: negative predictive value. Figure 2: Alluvial plot showing reclassification of patients using CACS-CL. The proportion of very low likelihood increased from 22.0% to 34.5%. Three different diagnostic algorithms Reclassification across risk categories