August 21st, 2012

Cardiovascular Risk Prediction: Two More Studies, Little Progress

Two studies published in JAMA provide new data — and, perhaps, some additional clarity — about using additional markers to help improve risk prediction for coronary heart disease (CHD) and cardiovascular disease (CVD).

In one study, Joseph Yeboah and colleagues used data from 1330 intermediate-risk participants in the Multi-Ethnic Study of Atherosclerosis (MESA)  to analyze the prognostic value of 6 risk markers: coronary artery calcium (CAC), carotid intima-media thickness (CIMT), ankle-brachial index (ABI), brachial flow-mediated dilation (FMD), high-sensitivity C-reactive protein (CRP), and family history of CHD.

After a median follow-up of 7.6 years, four risk markers (CAC, ABI, CRP, and family history) were found to be independent risk factors for CHD. CAC provided “the highest improvement in discrimination” over traditional risk scores. “The present study,” wrote the authors, “provides additional support for the use of CAC as a tool for refining cardiovascular risk prediction in individuals classified as intermediate risk.” However, “broad recommendations” about CAC should not be made until the associated problems of radiation exposure and incidental findings are addressed, they cautioned.

In the other study, Hester Den Ruijter and colleagues focused on CIMT, performing a meta-analysis in which they analyzed individual patient data from 14 studies and 45,828 patients. They found that adding CIMT provided only a small improvement in net reclassification which, they concluded, was “unlikely to be of clinical importance.”

In an accompanying editorial, J. Michael Gaziano and Peter Wilson write that “although there has been a great deal of work on the improvement in prediction modeling, less work has been done in 2 areas: the cost and risk in the screened population and risk prediction over time.” Using the example of an intermediate-risk patient who is a possible candidate for lipid-lowering therapy, they note that although CAC improves classification “at a single point in time,” most physicians evaluate patients over time and will often repeat tests to track trends over time. In this context, radiation exposure and costs may limit the utility of CAC.

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