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Incremental Prognostic Utility of Coronary CT Angiography for Asymptomatic Patients Based Upon Extent and Severity of Coronary Artery Calcium: Results From the Coronary CT Angiography EvaluatioN for Clinical Outcomes InteRnational Multicenter (CONFIRM) Study
Study Questions:
Is there a difference in the prognostic valve of coronary CT angiography (CCTA) in asymptomatic patients when stratified by coronary artery calcium score (CACS) severity?
Methods:
This was a prospective, multicenter, international cohort study of 3,217 asymptomatic patients without coronary artery disease who underwent CACS and CCTA. Patients were followed prospectively for 2.5 years for the primary outcome, a composite of all-cause mortality and nonfatal myocardial infarction (MI). Participants were classified as low (<10%), low-intermediate (10-15%), high-intermediate (16-20%), and high (>20%) risk according to the Framingham 10-year coronary heart disease risk scores (FRS). For each CACS category (0-10, 11-100, 101-400, 401-1,000, and >1,000), the incremental prognostic value, above and beyond the FRS, was determined with likelihood ratio, C-statistic, and continuous net reclassification improvement (NRI).
Results:
There were 58 composite endpoints in the analytic sample of 3,217 patients (1.8% over 2.5 years). The addition of CCTA to a model including the FRS significantly improved the prediction of the composite endpoint in individuals with a CACS >100. However, in patients with a CACS ≤100 the incremental value of CCTA over and above FRS was not significant. Furthermore, the incremental benefit of CCTA over FRS was particularly evident for those with a CACS between 101 and 400; the value was attenuated with higher CACS.
Conclusions:
CCTA improves prediction of future fatal and nonfatal events, over and above the Framingham risk score, in asymptomatic individuals with intermediately high (100-400 Agatston units) CACS.
Perspective:
This is an important study, which suggests that the prognostic value of CCTA does differ according to CACS severity. A major implication of the results is that CCTA does not reliably improve risk stratification in individuals with lower or higher CACS. The former population is at very low risk to start in any case and the lack of incremental prognostic benefit with CCTA is not surprising; in those with particularly high CACS, the diagnostic accuracy of CCTA may be limited by artifacts.
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