For patients whose cardiovascular risk falls into a gray area, a coronary artery calcium scan may provide the additional information needed to get a clearer picture of their risk, according to a new study published in JAMA.

The study examined whether adding coronary artery calcium (CAC) scores to the American Heart Association’s newer Predicting Risk of CVD Events (PREVENT) equations improves estimates of a person’s 10-year risk of atherosclerotic cardiovascular disease (ASCVD).

PREVENT is now recommended in the 2026 ACC/AHA/Multisociety Dyslipidemia Guideline, which classifies 10-year ASCVD risk as low (less than 3%), borderline (3% to less than 5%), intermediate (5% to less than 10%), or high (10% or greater). The guidelines recommend considering CAC testing for selected people at borderline or intermediate risk when decisions about lipid-lowering treatment remain uncertain.

To see how much CAC actually adds to PREVENT, researchers analyzed 6,098 adults ages 45 to 79 from the Multi-Ethnic Study of Atherosclerosis, a study of the characteristics of subclinical cardiovascular disease and the risk factors that predict progression to clinically overt cardiovascular disease or progression of the subclinical disease. None of the study participants had cardiovascular disease when they entered the study, which was initiated in 2000. Their average age was 61, 52% were women, and 49% had detectable coronary calcium. Over 10 years, 366 participants experienced an ASCVD event.

Across the full study population, knowing a person’s CAC score added relatively little. But the picture changed for people in the borderline-risk group. Their 10-year ASCVD event rate was just 1.9% when no coronary calcium was detected. It climbed to 3.9% with a CAC score between one and 99, 7.4% with a score between 100 and 299, and 14.3% with a score of 300 or higher.

Those differences translated into meaningful shifts in risk classification. Among borderline-risk participants who went on to have an ASCVD event, 50% were correctly moved into a higher-risk category after CAC was considered. Among those who remained event-free, 61% were correctly moved into a lower-risk category.

The findings suggest CAC may be most valuable as a targeted tool rather than something routinely added to cardiovascular risk assessment for everyone. The results also point toward a more individualized approach to cardiovascular prevention. Rather than simply adding another test, CAC could help determine when an initial risk estimate does not tell the whole story.

As the authors conclude, future research should focus on “refining the optimal use of CAC with the PREVENT-ASCVD equations” across different patient groups and stages of life.