Coronary artery calcium (CAC) scoring together with the Framingham method is more accurate for determining individuals' risks for coronary heart disease (CHD) than Framingham scores alone, a study published Oct. 19 in the Journal of the American College of Cardiology (JACC) concluded.
Several recent studies have investigated the prospect of using CAC scores, concomitantly with other risk-scoring algorithms like the Framingham risk score, to predict individuals' risks of coronary heart disease (CHD). The present study sought to further examine the potential of CAC scores to more accurately reclassify individuals' risks for CHD, while attempting to empirically derive cutoff points for risk reclassification.
A part of the Rotterdam study in the Netherlands, the study monitored 2,028 asymptomatic participants 55 years of age or older for a median follow-up time of slightly more than nine years. The researchers performed baseline electron-beam tomography (EBT) scans of all patients to assess CAC (employing Agatston's method) in the epicardial coronary arteries. Framingham risk scores also were calculated for all participants.
Eighty-one of the 2,028 participants experienced their first myocardial infarctions within the follow-up period, while 54 persons died from CHD. The median CAC score of the sample, comprised of 57 percent women and 43 percent men, was measured at 84 Agatston units (AU).
The researchers found that using CAC scores along with the Framingham method significantly improved the predictive accuracy for determining CHD risk, particularly for the intermediate-risk group in which treatment decisions are uncertain. Of the 451 participants classified in the intermediate-risk group using the Framingham method, 51 percent were reclassified, 30 percent to the low-risk group and 21 percent to the high-risk group.
Out of the 1,438 participants initially classified as low-risk for CHD, 12 percent were reclassified after including CAC scores, 11 percent to the intermediate group and 1 percent to the high-risk group. Additionally, 34 percent of the 144 participants in the high-risk group were reclassified, 29 percent to the intermediate-risk group and 5 percent to the low-risk group. Overall, more individuals were reclassified as having lower risks for CHD with the inclusion of CAC scoring.
For the intermediate Framingham risk group, which experienced the largest reclassification of individuals' risks, the authors determined a lower cutoff CAC score of 50 AU and an upper cutoff of 615 AU for reclassifying individuals into the low- and high-risk CHD groups, respectively.
"On the basis of CAC testing, more than 50 percent of an asymptomatic older population at intermediate risk [were] reclassified as having either low or high risk of hard CHD events," author Suzette E. Elias-Smale, MD, from the department of epidemiology at the Erasmus Medical Center in Rotterdam, the Netherlands, co-wrote with colleagues.
The authors admitted that their findings may be somewhat limited by their sample population, which was made up of asymptomatic older individuals, saying that the "results should not automatically be generalized to a younger population." They also emphasized the importance of additional randomized studies, especially to test this study's upper and lower Agatston CAC score cutoffs.
One important strength of the study was that none of the participants was notified of his CAC score, meaning that lifestyle changes resulting from the study effects would be minimal.
The authors concluded that "CAC scoring is a powerful method to reclassify persons into more appropriate [CHD] risk categories."