Coronary artery calcium score as a gatekeeper for further testing in patients with low pretest probability of obstructive coronary artery disease: A cost-effectiveness analysis

INTRODUCTION AND OBJECTIVES: Current guidelines recommend not routinely testing patients with chest pain and low pretest probability (PTP <15%) of obstructive coronary artery disease (CAD), but envisage the use of risk modifiers, such as coronary artery calcium score (CACS), to refine patient selection for testing. We aimed to assess the cost-effectiveness (CE) of three different testing strategies in this population: (A) defer testing; (B) perform CACS, withholding further testing if CACS=0, and proceeding to coronary CT angiography (CCTA) if CACS>0; (C) CCTA in all. METHODS: We developed a CE model using data from a two-center cross-sectional study of 1385 patients with non-acute chest pain and PTP <15% undergoing CACS followed by CCTA. Key input data included the prevalence of obstructive CAD on CCTA (10.3%), the proportion with CACS=0 (57%), and the negative predictive value of CACS for obstructive CAD on CCTA (98.1%). RESULTS: Not testing would correctly classify 89.7% of cases and at a cost of €121433 per 1000 patients. Using CACS as a gatekeeper for CCTA would correctly diagnose 98.9% of cases and cost €247116/1000 patients. Employing first-line CCTA would correctly classify all patients, at a cost of €271007/1000 diagnosed patients. The added cost for an additional correct diagnosis was €1366 for CACS±CCTA vs. no testing, and €2172 for CCTA vs. CACS±CCTA. CONCLUSIONS: CACS as a gatekeeper for further testing is cost-effective between a threshold of €1366 and €2172 per additional correct diagnosis. CCTA yields the most correct diagnoses and is cost-effective above a threshold of €2172.