Objective We evaluated coronary artery calcium (CAC) scoring as an initial diagnostic tool in outpatients and in patients presenting at the emergency department due to suspected coronary artery disease (CAD).

Methods 10 857 patients underwent CAC scoring and coronary CT angiography (CCTA) at Haukeland University Hospital in Norway during 2013–2020. Based on CCTA, obstructive CAD was defined as at least one coronary stenosis ≥50%. High-risk CAD included obstructive stenoses of the left main stem, the proximal left ascending artery or affecting all three major vascular territories with at least one proximal segment involved.

Results Median age was 58 years and 49.5% were women. The overall prevalence of CAC=0 was 45.0%. Among those with CAC=0, 1.8% had obstructive CAD and 0.6% had high-risk CAD on CCTA. Overall, the sensitivity, specificity, positive predictive value and negative predictive value (NPV) of CAC=0 for obstructive CAD were 95.3%, 53.4%, 30.0% and 98.2%, respectively. However, among patients <45 years of age, although the NPV was high at 98.9%, the sensitivity of CAC=0 for obstructive CAD was only 82.3%.

Conclusions In symptomatic patients, CAC=0 correctly ruled out obstructive CAD and high-risk CAD in 98.2% and 99.4% of cases. This large registry-based cross-sectional study supports the incorporation of CAC testing in the early triage of patients with chest pain and as a gatekeeper to further cardiac testing. However, a full CCTA may be needed for safely ruling out obstructive CAD in the youngest patients (<45 years of age).