Old test: new twist.

The primary use of coronary artery calcium scoring has been in its ability to predict coronary artery disease (CAD) events in generally asymptomatic patients and to provide incremental risk stratification beyond the use of traditional clinical risk factor assessment. Thresholds of calcium burden, as determined by the area-density scoring or Agatston scoring method, on the basis of age, sex, and race, provide a reference for physicians in regard to risk, with more extensive coronary artery calcium (CAC) associated with increased risk of subsequent future events. This prognostic value of CAC has been well established and can be incorporated into the overall risk assessment to modify clinical management. There is no doubt that cardiac CT can detect subclinical atheroma. CAC is almost 100% indicative of the presence of some degree of atherosclerosis, either non-obstructive or obstructive. For obstructive CAD, the sensitivity of any coronary artery calcium is high. However, CAC has not been widely used as the sole test to diagnose obstructive CAD in that a tradeoff exists for the test sensitivity and specificity on the basis of the threshold used for defining the presence or absence of disease. Indeed, the presence of calcium is not 100% specific for identification of a significant, flow-limiting coronary artery lesion, and overall specificities and the positive predictive values are low. Reasons for this limited predictive accuracy include limitations of prior studies by biases such as verification bias and referral bias. Importantly, the lesion calcification can be influenced by many factors, including prior plaque instability and healing, age, and inflammation such that, although the extent of total calcium in a patient is generally related to the atherosclerotic burden, there can be significant variability between arteries and within any given individual plaque. It is important to recognize that a positive calcium score (score . 0) is most often not associated with significant obstructive CAD. However, a calcium score of 0 does not exclude the presence of atherosclerotic plaques or obstructive disease, particularly in symptomatic persons. In this issue of the Journal, Qian et al report on vessel and lesion calcium score in comparison to total CAC score for the diagnosis of obstructive CAD. In this small retrospective study of patients undergoing calcium scoring and