10-Year Coronary Heart Disease Risk Prediction Using Coronary Artery Calcium and Traditional Risk Factors

Background Several studies have demonstrated the tremendous potential of using coronary artery calcium (CAC) in addition to traditional risk factors for coronary heart disease (CHD) risk prediction. However, to date no risk score incorporating CAC has been developed. Objectives Our goal was to derive and validate a novel risk score to estimate 10-year CHD risk using CAC and traditional risk factors. Methods Algorithm development was conducted in the Multi-Ethnic Study of Atherosclerosis (MESA), a prospective community-based cohort study of 6814 participants aged 45–84, free of clinical heart disease at baseline and followed for 10 years. MESA is gender balanced and included 39% Non-Hispanic whites, 12% Chinese American, 28% African American, and 22% Hispanic Americans. External validation was conducted in the Heinz Nixdorf Recall Study (HNR) and the Dallas Heart Study (DHS). Results Inclusion of CAC in the MESA risk score offered significant improvements in risk prediction (C-statistic 0.80 versus 0.75, p<0.0001). External validation in both HNR and DHS provided evidence of very good discrimination and calibration. Harrell’s C-statistic was 0.779 in HNR, and 0.816 in DHS. Additionally the difference in estimated 10-year risk between events and non-events was approximately 8–9%, indicating excellent discrimination. Mean calibration, or calibration-in-the-large, was excellent for both studies, with average predicted 10-year risk within half a percent of the observed event rate. Conclusions An accurate estimate of 10-year CHD risk can be obtained using traditional risk factors and CAC. The MESA risk score, which is available online on the MESA web site for easy use, can be used to aid clinicians in the communication of risk to patients and when determining risk-based treatment strategies.