Coronary Artery Calcium Scores Aid in Cardiovascular Risk Prediction

Laurie Barclay, MD

Jan. 13, 2004 — Coronary artery calcium scores (CACS) have predictive value over the Framingham Risk Score (FRS) for cardiovascular risk prediction in asymptomatic individuals, according to the results of a prospective, observational, population-based study published in the Jan. 14 issue of The Journal of the American Medical Association . Interestingly, this study shows that persons with CACS of 0 may still be at risk for myocardial infarction (MI).

"Guidelines advise that all adults undergo coronary heart disease (CHD) risk assessment to guide preventive treatment intensity," write Philip Greenland, MD, from Northwestern University in Chicago, Illinois, and colleagues. "Although the FRS is often recommended for this, it has been suggested that risk assessment may be improved by additional tests such as CACS."

In this study, 1,461 asymptomatic adults older than 45 years with at least one coronary risk factor were screened between 1990 to 1992, received computed tomography scanning and yearly telephone or clinic follow-up for up to 8.5 years, and were assessed for CHD. CACS results were analyzed in 1,312 subjects; 269 participants with diabetes and 14 participants with incomplete data or who had a coronary event before CACS were excluded.

During a median of 7.0 years of follow-up, the main outcome measure of nonfatal MI or CHD death occurred in 84 patients, and 70 patients died from any cause. FRS was more than 20% in 291 subjects (28%), and CACS was over 300 in 221 subjects (21%).

The risk of MI or CHD death was 14 times greater in subjects with an FRS of more than 20% than in subjects with an FRS of less than 10% (hazard ratio [HR], 14.3; 95% confidence interval [CI], 2.0 - 104; P = .009). Risk was fourfold greater in subjects with a CACS more than 300 than in subjects with a CACS of 0 (HR, 3.9; 95% CI, 2.1 - 7.3; P < .001). Across FRS categories, CACS predicted risk in subjects with an FRS greater than 10% ( P < .001) but not in subjects with an FRS less than 10%.

Study limitations include a study cohort that may not be heterogeneous or representative of the general population, limited applicability to women and nonwhite ethnic groups, failure to determine if CACS measurement allowed for improved clinical outcomes, and possible effect of motivational factors.

"These data support the hypothesis that high CACS can modify predicted risk obtained from FRS alone, especially among patients in the intermediate-risk category in whom clinical decision making is most uncertain," the authors write. "A CACS does not appear to change predicted risk substantially enough for people with an FRS of less than 10% or an FRS of 20% or more to modify the overall clinical approach, as currently recommended by the National Cholesterol Education Program."

The National Heart, Lung, and Blood Institute supported this study.

JAMA. 2004;291:210-215

Reviewed by Gary D. Vogin, MD