Abstract
BACKGROUND: The diagnostic accuracy of coronary computed tomography angiography (CTA) for obstructive coronary artery disease (CAD) is influenced by the extent of coronary artery calcium (CAC). Incidental CAC findings on non-gated chest computed tomography (CT) may inform the selection of patients for subsequent coronary CTA. The purpose of this study was to evaluate how incidental CAC findings on non-gated chest CT affect the diagnostic accuracy of coronary CTA for obstructive CAD. METHODS: We retrospectively identified consecutive patients who underwent coronary CTA. Cases who underwent both chest CT and invasive coronary angiography (ICA) within 1 year of the coronary CTA were included. The severity of CAC on non-gated chest CT was assessed using a semi-quantitative scoring system and classified into four scales (absent, mild, moderate, severe). The area under the receiver operating characteristic (ROC) curve (AUC) was used to evaluate the diagnostic accuracy of coronary CTA compared to ICA. Subgroups were stratified based on the severity of CAC, and the accuracy of coronary CTA diagnosis in each subgroup was analyzed. RESULTS: A total of 337 patients were included. The overall AUC of coronary CTA for diagnosing obstructive CAD was 0.609. In patients with absent or mild CAC, the AUC values were higher than the overall AUC (0.650 and 0.665, respectively). In contrast, among patients with moderate or severe CAC, the AUC decreased to 0.549 and 0.491, respectively. Notably, in the severe CAC subgroup, the AUC fell below 0.5, indicating no diagnostic value. The proportion of obstructive CAD was significantly higher in the severe CAC subgroup compared to the other groups (P=0.004), and the negative predictive value of coronary CTA dropped to 0. CONCLUSIONS: In patients with severe CAC on non-gated chest CT, coronary CTA is less effective in providing accurate stenosis assessment. However, the cut-off values for semi-quantitative CAC scoring remain to be clearly defined through future studies.