USPSTF dismisses CAC for heart disease risk assessment

2016 12 01 17 10 35 256 Pulmonary Trunk Heart 400

The U.S. Preventive Services Task Force (USPSTF) has reaffirmed its recommendation against using nontraditional factors -- including coronary artery calcium (CAC) score -- to assess the risk of heart disease, in a statement published online July 10 in the Journal of the American Medical Association.

In a recent draft, the USPSTF claimed that there was insufficient evidence to justify adding CAC, ankle-brachial index (ABI), or high-sensitivity C-reactive protein (hsCRP) to traditional risk factors already being used to determine which patients might be at risk of cardiovascular events.

Though these nontraditional risk factors have demonstrated a capacity to slightly improve discrimination and risk classification for heart disease, a subsequent report highlighted key gaps in evidence regarding their benefit:

  • The clinical implications of any improvement in patient risk assessment remain unknown.
  • Treatment decisions guided by the markers have not been shown to reduce cardiovascular events.
  • Their addition to the markers of the pooled cohort equations (PCE) risk estimator is modest.

Therefore, the USPSTF has decided to maintain its preliminary ruling against the inclusion of these new factors into routine clinical risk assessment. However, the task force did acknowledge that CAC was far more likely than the other two nontraditional risk factors to provide meaningful alterations in patients' estimated risk.

Numerous researchers have further suggested that risk assessment with CAC is strong enough to warrant a more positive recommendation apart from the other factors.

Several studies have shown that CAC was highly beneficial when used selectively for patients whose treatment decisions remained unclear after initial testing -- especially for adults whose risk estimates were slightly above 7.5%, wrote Dr. Philip Greenland from Northwestern University and Dr. Tamar Polonsky from the University of Chicago in an editorial in JAMA Cardiology.

"CAC testing is most valuable for the many adults at the borders of current treatment thresholds and to clarify decisions about whether to start or to intensify therapy," they wrote. "The use of CAC testing could help identify a large proportion of adults who are otherwise statin-eligible in whom long-term drug therapy might safely be avoided."

To achieve a grade A or B recommendation for the use of CAC for these intermediate-risk patients, the USPSTF emphasized the need for a large-scale randomized clinical trial.

"Undoubtedly, [a large-scale clinical trial] would be expensive, but it would be a wise investment because it would help to refine current clinical testing strategies to identify patients who will benefit most from primary prevention interventions," wrote Dr. John Wilkins and Dr. Donald Lloyd-Jones from Northwestern University in an additional editorial in JAMA.

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