Integrating Coronary Calcium into Risk Prediction: Current Approaches and Future Directions

Alan Boyar

Abstract

The CT coronary calcium score is a predictor of risk for cardiovascular events. Individuals without detectable coronary calcium are at very low risk for events whereas individuals with large amounts of coronary calcium have annual event rates of 4.8%. In the USA the Framingham scoring system is the most widely used method for calculating cardiovascular event risk. To date at least four approaches have been proposed to combine risk determined from the CT coronary calcium score with the Framingham scoring system risk. These include: 1) adjustment of age points in the Framingham scoring system based on CT coronary calcium age-sex percentile rank (determined from a nonogram of CT coronary calcium scores); 2) age replacement in the Framingham scoring system in which an “arterial age” determined by the CT coronary calcium score replaces chronological age; 3) a likelihood or hazard ratio approach; and 4) Bayesian methods for risk combination. This review will discuss methods and merits of each of these approaches. With the exception of the age-sex percentile rank method which suffers from specific intrinsic problems, none of the other approaches is necessarily superior; ultimately, the one that is easiest to use and most reliable will probably be the one adopted for clinical use.

Keywords: cardiovascular risk, CT coronary calcium score, framingham