IMPORTANCEThe diagnostic value is unclear of a 0 coronary artery calcium (CAC) score to rule out obstructive coronary artery disease (CAD) and near-term clinical events across different age groups.OBJECTIVE To assess the diagnostic value of a CAC score of 0 for reducing the likelihood of obstructive CAD and to assess the implications of such a CAC score and obstructive CAD across different age groups. DESIGN, SETTING, AND PARTICIPANTSThis cohort study obtained data from the Western Denmark Heart Registry and had a median follow-up time of 4.3 years. Included patients were aged 18 years or older who underwent computed tomography angiography (CTA) between