Carotid intima-media thickness (CIMT) and the presence or absence of plaque improve coronary heart disease (CHD) risk prediction when added to traditional risk factors (TRF), a US study has found.
CIMT and plaque presence are independently associated with CHD, but there have been limited data evaluating whether their addition to risk models can improve prediction. Vijay Nambi, from Baylor College of Medicine in Houston, Texas, and colleagues note the importance of improving current risk models, given that most CHD events occur in "low" and "intermediate" risk groups. The researchers used four risk prediction models to group a sample of 13,145 patients participating in the ARIC (Atherosclerosis Risk In Communities) study into those at low (<5% risk), intermediate (5–20% risk), or high (>20%) risk for CHD. The four prediction models considered TRF only, TRF plus CIMT,TRF plus plaque, and TRF plus CIMT plus plaque. Over a mean follow-up period of 15.1 years, there were 1812 incident CHD events, comprising 867 definite or probable myocardial infarctions, 159 CHD deaths, 688 coronary revascularizations, and 98 silent (electrocardiography-confirmed) myocardial infarctions. 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 individuals reclassified with the addition of CIMT and plaque information was determined. Observed events were compared with expected events, and the net reclassification index was calculated. The researchers report that approximately 23% of patients were reclassified by adding CIMT plus plaque information to TRF, with a net reclassification improvement of 9.9% Overall, the TRF pus CIMT plus plaque model provided the greatest improvement in AUC, increasing it from 0.742 with TRF only to 0.755. Individual additions of increased CIMT and plaque to TRF increased the AUC from 0.0742 to 0.750 and 0.751, respectively. The researchers note, however, that adding CIMT alone to TRF did not significantly improve model predictivity in women, adding plaque to TRF had a more pronounced effect. Writing in the Journal of the American College of Cardiology, the researchers conclude: improves CHD risk prediction... and should be considered in the intermediate risk group.”They recommend: "Ultrasound-based risk stratification strategies should be tested in clinical trials to evaluate whether improved prevention of cardiovascular events is possible." James Stein and Heather Johnson, from the School of Medicine and Public Health in Madison, Wisconsin, USA commented in a related editorial that the study "opens the door for outcomes research studies that are required to determine if atherosclerosis imaging truly is as helpful as its proponents believe." Read the abstract
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