Abstract 1010: Net Reclassification Improvement is Particularly High When Coronary Artery Calcium Scoring is Focused on Intermediate Risk Subjects: The Heinz Nixdorf Recall Study
Background: Coronary artery calcium (CAC) has been suggested to improve prediction of coronary events beyond traditional risk factor assessment. However, net reclassification improvement (NRI) beyond traditional risk factor assessment using CAC has thus far not been shown.
Methods: In 4129 subjects without known coronary artery disease from the general population, traditional risk factors and CAC were measured. Subjects were stratified into 3 risk categories using the Framingham risk score (FRS, low, intermediate, high). Subjects were followed for 5 years for coronary death and non-fatal myocardial infarction.
Results: Risk of coronary events significantly increased with increasing FRS- and CAC score categories (Fig. 1⇓). Cumulative risk in 5 years increased from 1.16 in subjects with CAC<100, to 3.31 in those with CAC=100 –399, to 8.27 in those with CAC≥400 (p<0.0001). Adding log(CAC+1) to the FRS improved the area under the ROC curve (AuC) from 0.681 to 0.749 (p=0.003). When reclassifying risk in intermediate risk subjects, 17 subjects with events were reclassified correctly, while 12 subjects were incorrectly reclassified. Among intermediate risk subjects who did not experience events, 812 were correctly reclassified into a lower risk category, whereas 175 subjects were incorrectly reclassified into a higher risk category. The NRI relating to the entire cohort was estimated at 21% (p=0.0003). NRI in intermediate risk subjects only was estimated at 63% (p<0.0001).
Conclusion: Adding CAC scoring to the FRS results in a significant net reclassification improvement of coronary risk, especially when focused on intermediate risk subjects.