Greenland P, LaBree L, Azen SP, et al: Coronary artery calcium score combined with Framingham score for risk prediction in asymptomatic individuals. JAMA 2004;291(2):210-15.
Mitka M: Standards set for CT calcium screening but its clinical value remains unclear. JAMA 2004;291(4):408-411.
Computed tomography (CT) to measure coronary artery calcium scoring (CACS) is being aggressively marketed to screen for coronary artery disease, although its clinical value remains unclear. The authors studied whether CAC assessment, combined with Framingham Risk Score (FRS), provided predictive information that was superior to either method alone. Between 1990 and 1992, providers screened with CACS and FRS 1,461 asymptomatic adults without diabetes, but with coronary risk factors. During 7 years of follow-up, 84 patients experienced MI or coronary heart disease (CHD) death. Compared with an FRS of <10%, a score of >20% predicted the risk of MI or CHD death (hazard ratio = 14.3). CAC scores were categorized as 0, 1-100, 101-300, or >300. Compared to a score of 0, a score >300 predicted MI or CHD death (HR = 3.9). For patients with an FRS of <10% or an FRS of >20%, the CACS did not change the predicted risk substantially. Even in the absence of CAC (score = 0), 14 of 316 participants had MI or CHD death during the study.
In this study, CACS improved the accuracy of FRS predictions only in participants whose FRS was between 10% to 19%. For these persons, a CACS >300 was associated with an added CHD event risk. These study results will not settle the controversy about whether CACS is able to motivate patients to modify their CAD risk factors in a manner that makes it worth the cost and effort.