In July 2018, the U.S. Preventive Services Task Force (USPSTF) stated the need for more evidence from large-scale trials before recommending the use of nontraditional factors -- including CT CAC -- to assess an individual's risk of heart disease. The task force highlighted the potential for these factors to overestimate heart disease risk, which could lead to unnecessary testing and medication. This ultimately led the USPSTF to give CT calcium assessment an "I" grade.
Nonetheless, the AHA and ACC published a new guideline in November 2018 that assigned a class IIA recommendation to CT CAC testing for individuals at risk of developing atherosclerotic cardiovascular disease. The societies based this decision on numerous studies demonstrating the potential benefits of CT CAC for at-risk individuals -- particularly for adults ages 40 to 75 with a 5% to 20% 10-year risk.
"The 2018 AHA/ACC prevention guideline offers something fundamentally new for these patients ... more definitive risk stratification (that is, to move patients both up and down the risk spectrum)," senior author Dr. Michael Blaha and colleagues from Johns Hopkins University wrote in their opinion article.
CT CAC has the ability to properly classify individuals at the highest risk for atherosclerotic cardiovascular disease -- proving to be "consistently better at prognosticating, discriminating, calibrating, and reclassifying atherosclerotic cardiovascular disease than using traditional risk scores," they wrote.
In addition, a CT CAC score of 0 indicates a very low risk for future cardiac events, and clinicians may be able to reclassify intermediate-risk patients with a score of 0 into a lower category for which statin therapy is not recommended.
"It is critical that the main stakeholders, especially primary care physicians, understand the newly proposed role for [CT] CAC testing and do not equate it with screening," the authors wrote. "Rather than bringing in many additional statin candidates, this testing should serve as a decision aid to 'derisk' certain patients and distinguish those who may benefit from preventive pharmacologic therapies."
Still, the decision to rely on CT CAC is not always straightforward, and clinical judgment and patient preferences should stand at the forefront of decision-making, according to Blaha and colleagues. Clinicians should ensure that patients are aware of the radiation exposure (roughly 1 mSv) associated with the test as well as its up-front monetary costs, although recent analyses have confirmed that selective use of CT CAC is more cost-effective than recommending statin therapy as a "treat-all" approach for intermediate-risk patients.
"The next step for [CT] CAC testing in primary prevention is clearly universal coverage for appropriate candidates ... [with] reasonable pricing (< $150)," they wrote. "This testing can reduce low-value treatment and focus primary prevention therapy on those most likely to benefit."
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