A new meta-analysis evaluating the predictive power of coronary artery calcium (CAC) scores as detected by electron-beam computed tomography (EBCT) indicates that calcium scores provide information in addition to what can be extrapolated from standard risk factors.

"CAC scores are associated with CHD events, even when other CHD risk factors are accounted for," Dr Mark J Pletcher (University of California, San Francisco) and colleagues write in the June 28, 2004 issue of the Archives of Internal Medicine.[1]

Calcium scores and CHD risk

To get a better idea, Pletcher et al conducted a literature review of all EBCT/CAC studies in asymptomatic patients, ultimately limiting the search to four studies that met their inclusion criteria. When CAC scores were arbitrarily divided into groups of 1-100, 101-400, and >400, the authors report that relative risk estimates increased with higher scores; however, the degree of risk varied widely between studies. Pletcher and colleagues hypothesize that heterogeneity between studiesincluding factors such as tomographic slice thickness, proportion of female subjects, blinded/unblinded adjudication, means of measuring other risk factors, etcmay have accounted for the different study findings.

Relative risk of coronary events by CAC score

CAC score Risk ratio 95% CI p 1-100 2.1 1.6-2.9 <0.001 101-400 5.4 2.2-13 <0.001 >400 10 3.1-34 <0.001

Overall, however, they conclude, "the relative risks associated with increasing CAC score are at least as large as those associated with established CHD risk factors."

They continue, "We believe our meta-analysis has already answered one important, unresolved question: Does the CAC score predict coronary events even when standard CHD risk factors are taken into account? The answer, at least among the populations represented in these studies, is yes."