Incremental prognostic value of coronary artery calcium score versus CT angiography among symptomatic patients without known coronary artery disease.

OBJECTIVE: To evaluate the prognostic value and test characteristics of coronary artery calcium (CAC) score for the identification of obstructive coronary artery disease (CAD) in comparison with coronary computed tomography angiography (CCTA) among symptomatic patients.

METHODS: Retrospective cohort study at two large hospitals, including all symptomatic patients without prior CAD who underwent both CCTA and CAC. Accuracy of CAC for the identification of ≥ 50% and ≥ 70% stenosis by CCTA was evaluated. Prognostic value of CAC and CCTA were compared for prediction of major adverse cardiovascular events (MACE, defined as non-fatal myocardial infarction, cardiovascular death, late coronary revascularization (>90 days), and unstable angina requiring hospitalization).

RESULTS: Among 1145 included patients, the mean age was 55 ± 12 years and median follow up 2.4 (IQR: 1.5-3.5) years. Overall, 406 (35%) CCTA were normal, 454 (40%) had <50% stenosis, and 285 (25%) had ≥ 50% stenosis. The prevalence of ≥ 70% stenosis was 16%. Among 483 (42%) patients with CAC zero, 395 (82%) had normal CCTA, 81 (17%) <50% stenosis, and 7 (1.5%) ≥ 50% stenosis. 2 (0.4%) patients had ≥ 70% stenosis. For diagnosis of ≥ 50% stenosis, CAC had a sensitivity of 98% and specificity of 55%. The negative predictive value (NPV) for CAC was 99% for ≥ 50% stenosis and 99.6% for ≥ 70% stenosis by CCTA. There were no adverse events among the 7 patients with zero calcium and ≥ 50% CAD. For prediction of MACE, the c-statistic for clinical risk factors of 0.62 increased to 0.73 (p < 0.001) with CAC versus 0.77 (p = 0.02) with CCTA.

CONCLUSION: Among symptomatic patients with CAC zero, a 1-2% prevalence of potentially obstructive CAD occurs, although this finding was not associated with future coronary revascularization or adverse prognosis within 2 years.