Direct comparison between coronary computed tomography and invasive angiography for calculation of SYNTAX score

Aims: We aimed to test the feasibility of calculating SYNTAX score from coronary computed tomographic angiography (CCTA) compared to from invasive coronary angiography (ICA). Methods and results: SYNTAX score was independently and blindly calculated from CCTA and from ICA in 104 patients, age 57+/-10, with significant (>50%) stenoses in 1.7+/-0.7 vessels. The level of agreement was assessed by Cohen's kappa. Agreement between ICA and CCTA for conventional vessel-based analysis (presence of >50% stenosis per vessel) was substantial with kappa=0.66 and sensitivity, specificity and accuracy of 74%, 90% and 80%, respectively. The mean SYNTAX score was 14.2+/-10.0 by ICA and 10.3+/-6.9 by CCTA, with a significant underestimation of 3.9+/-8.2 by CCTA (p<0.001). Weighted kappa was 0.33, indicating only fair agreement. When only good quality CCTA were included, kappa improved to 0.56. Analysis of the cause of the bias showed ICA to identify more lesions per patient (2.2+/-1.3 vs. 1.7+/-1.0, p<0.001), while the mean score per lesion was not different (6.4 vs. 5.9, p=ns). Conclusions: CCTA, despite having a good agreement with ICA by conventional vessel-based analysis, showed only fair agreement for the calculation of SYNTAX score, and cannot be currently used as a substitute for diagnostic ICA for this purpose.