Pre- and post-test probability of obstructive coronary artery disease in two diagnostic strategies: Relative contributions of exercise ECG and coronary CT angiography

Introduction: The aim of this study was to assess the change in the theoretical probability of coronary artery disease (CAD) in patients with suspected CAD undergoing coronary computed tomographic angiography as the first-line test compared to CCTA after an exercise ECG. Methods: Pre- and post-test probabilities of CAD were assessed in 158 patients with suspected CAD undergoing dual-source CCTA as the first-line test (Group A) and in 134 in whom CCTA was performed after an exercise ECG (Group B). Pre-test probabilities were calculated based on age, gender and type of chest pain. Post-test probabilities were calculated according to Bayes’ theorem. Results: There were no significant differences between the groups regarding pre-test probability (median 23.5% [13.3---37.8] in group A vs. 20.5% [13.4---34.5] in group B; p=0.479). In group A, the percentage of patients with intermediate likelihood of disease (10---90%) was 90% before testing and 15% after CCTA (p<0.001), while in group B, it was 95% before testing, 87% after exercise ECG (p=NS), and 17% after CCTA (p<0.001). Conclusion: Unlike exercise testing, CCTA is able to reclassify risk in the majority of patients with an intermediate likelihood of obstructive CAD. The use of CCTA as the first-line diagnostic test for CAD may be advantageous in this setting. © 2012 Sociedade Portuguesa de Cardiologia. Published by Elsevier Espana, S.L. All rights reserved.