Abstract 1013: Does Carotid Intima-Media Thickness Improve Cardiovascular Risk Prediction?
Background: Non-invasive measures of atherosclerosis, such as IMT, may improve global cardiovascular risk prediction.
Objective: To determine whether IMT in addition to traditional risk factors improves classification of persons into clinically established risk categories.
Methods: Within the Rotterdam study, a population-based cohort study, 4,136 non-diabetic persons (1,589 men and 2,547 women) aged 55– 80 years and free of CVD at baseline were followed up for a median time of 12.1 years for hard cardiovascular endpoints. Compared to gender-specific models based on Framingham risk factors, we studied the ability of IMT measurement to better classify persons into categories of low (<10%), intermediate (10 –20%) and high (>20%) 10-year risk of CVD.
Results: In women, addition of IMT to Framingham risk factors significantly improved risk classification. IMT improved the C-statistic of the model from 0.728 to 0.737 (p<0.0001), indicating a slightly better discriminative ability, at good calibration (good agreement between observed and predicted risk across risk categories). Of women categorized as low risk based on Framingham risk factors, 6% (n=91) were reclassified to the intermediate risk category by additional IMT measurement. Of women at intermediate risk, 16% (n=107) were downgraded to low risk and 14% (n=88) upgraded to high risk. Of women at high risk, 19% (n=83) were downgraded to the intermediate risk category. The net reclassification improvement (NRI) was 7.01% (p<0.01) indicating a true reclassification improvement by addition of IMT. However, percentages of persons correctly upgraded in risk by IMT measurement were relatively small compared to the percentages of persons correctly downgraded in risk. In men, addition of IMT to Framingham risk factors did not improve cardiovascular risk prediction (both C-statistic and NRI non-significant).
Conclusions: In men, IMT measurement did not significantly improve risk stratification based on traditional risk factors. In women, IMT showed a modest ability to reclassify persons to a more accurate cardiovascular risk category. The clinical usefulness of IMT to improve cardiovascular risk stratification warrants further study.