Carotid Intima-Media Thickness and Presence or Absence of Plaque Improves Prediction of Coronary Heart Disease Risk

OBJECTIVES: We evaluated whether carotid intima-media thickness (CIMT) and the presence or absence of plaque improved coronary heart disease (CHD) risk prediction when added to traditional risk factors (TRF). BACKGROUND: Traditional CHD risk prediction schemes need further improvement as the majority of the CHD events occur in the "low" and "intermediate" risk groups. On an ultrasound scan, CIMT and presence of plaque are associated with CHD, and therefore could potentially help improve CHD risk prediction. METHODS: Risk prediction models (overall, and in men and women) considered included TRF only, TRF plus CIMT, TRF plus plaque, and TRF plus CIMT plus plaque. Model predictivity was determined by calculating the area under the receiver-operating characteristic curve (AUC) adjusted for optimism. Cox proportional hazards models were used to estimate 10-year CHD risk for each model, and the number of subjects reclassified was determined. Observed events were compared with expected events, and the net reclassification index was calculated. RESULTS: Of 13,145 eligible subjects (5,682 men, 7,463 women), approximately 23% were reclassified by adding CIMT plus plaque information. Overall, the CIMT plus TRF plus plaque model provided the most improvement in AUC, which increased from 0.742 (TRF only) to 0.755 (95% confidence interval for the difference in adjusted AUC: 0.008 to 0.017) in the overall sample. Similarly, the CIMT plus TRF plus plaque model had the best net reclassification index of 9.9% in the overall population. Sex-specific analyses are presented in the manuscript. CONCLUSIONS: Adding plaque and CIMT to TRF improves CHD risk prediction in the ARIC (Atherosclerosis Risk In Communities) study.