Abstract Body (Do not enter title and authors here): Background It is unknown whether risk stratification in primary prevention is improved by adding coronary computed tomography angiography (CCTA)-derived data on coronary atherosclerosis to traditional risk factors and coronary artery calcification score (CACS).

Methods We used CCTA to assess the extent and/or presence of calcified and noncalcified coronary atherosclerosis (segment involvement score [SIS]) and obstructive disease (stenosis ≥50%) in 24,791 individuals without previous cardiovascular disease selected from a randomly recruited general population (the Swedish CArdioPulmonary bioImage Study [SCAPIS]). We also measured CACS and used traditional risk factors to calculate cardiovascular risk by the pooled cohort equation (PCE). The primary outcome was a composite of first occurrence of nonfatal myocardial infarction or death from coronary heart disease. We used four Cox regression models. First, the risk score (PCE) was entered as a continuous variable (Model 1). In Model 2, we added CACS to PCE. In Model 3, we added CCTA data to PCE. Finally, we added both CACS and CCTA data to PCE (Model 4).

Results During a median follow-up of 7.8 years, 304 coronary events occurred. SIS 3–4 and >4 were present in 9.6% and 7.9% of the population and were associated with adjusted hazard ratios of 2.71 (95% confidence interval [CI] 1.34–5.44) and 5.27 (95% CI 2.50–11.07), respectively (Figure 1 and Table 1). In a model based on PCE and CACS (Model 4), CCTA-derived data improved risk prediction (C-statistic improved from 0.764 to 0.779, p<0.01, Figure 2) and risk reclassification (net reclassification improvement of 0.150, 95% CI 0.052–0.240) and conferred a net correct upward reclassification of 7.5% in those with events and a net correct downward reclassification of 6.1% in those without events. In the subgroup defined as moderate risk by PCE and CACS, addition of CCTA data resulted in a net correct upward classification of 16.3% and a net correct downward classification of 20.4%.

Conclusion In a large cohort of individuals without established cardiovascular disease selected from a randomly recruited general population, the addition of CCTA-derived data on coronary atherosclerosis provides value beyond traditional risk factors and CACS in identifying individuals at risk of coronary events and in need of primary prevention.