Coronary Artery Calcium Score and Cardiovascular Event Prediction—Reply

In Reply: We agree with Drs Diederichsen and Mickley that reporting CACS to patients may cause anxiety, and this issue should be studied further. We have no data on this to report. We disagree that CACS is not able to discriminate between those who will and will not experience CHD events. Diederichsen and Mickley cite as evidence that a large proportion of adults have coronary calcium. However, we did not simply use a CACS greater than 0 to classify risk. Each participant's CACS was incorporated into a Cox proportional hazards model based on traditional risk factors. As we reported, with addition of CACS to the model there was a significant increase in the area under the receiver operating characteristic curve compared with the model based on traditional risk factors alone (0.76 vs 0.81, P < .001). This demonstrates a substantial improvement in model discrimination. Furthermore, addition of CACS to the basic model classified more individuals who experienced and did not experience events as high and low risk, respectively. We refer Diederichsen and Mickley to a previous article from the Multi-Ethnic Study of Atherosclerosis by Detrano et al¹ for event rates stratified by CACS, as they requested.