A large 10-year study published in JAMA suggests that coronary calcium scan benefit is far narrower than is commonly assumed, adding only a modest improvement over a standard risk calculator for most adults but providing more meaningful information for those whose risk sits in a middle band.
The research, from Northwestern University Feinberg School of Medicine, examined data from more than 6,000 adults aged 45 to 79 who took part in the Multi-Ethnic Study of Atherosclerosis. Each participant received both a coronary artery calcium (CAC) score and an estimate from PREVENT, the American Heart Association’s primary cardiovascular risk calculator, at the start of the study. Researchers then tracked outcomes over the following decade.
What the discrimination scores actually showed
Over ten years, 6% of participants experienced a heart attack or stroke. When the team compared risk models that included CAC scores against PREVENT alone, the gain was small: the model’s discrimination score, which measures how well it distinguishes between those who will and will not have a cardiovascular event, rose from 0.73 using PREVENT to 0.75 when CAC scores were added. That is a real, if modest, improvement, and the researchers are not claiming the scans are useless. But for a test that is growing in popularity, the margin is worth scrutinising.
The picture shifted when the analysis focused on patients whose PREVENT scores placed them in the borderline or intermediate risk categories. Study senior author Dr Nilay Shah, assistant professor of medicine in the division of cardiology at Northwestern University Feinberg School of Medicine, said that for these patients, the calcium score ‘can help determine whether their risk is actually lower or higher than initially estimated, which can help guide treatment decisions.’
Understanding those categories matters. According to STAT News, PREVENT classifies 10-year cardiovascular risk as low (under 3%), borderline (3% to 5%), intermediate (5% to 10%), and high (10% or above). The study used a combined borderline-to-intermediate band of 3% to 9% as its focus group. It is precisely this uncertain middle ground where the scan appeared to earn its place.
Coronary calcium scan benefit is not universal, researchers warn
Shah was direct about the limits of routine scanning. ‘Routinely using a calcium scan in people who are at low risk may result in unnecessary radiation exposure, testing and costs with unclear clinical benefits,’ he said. At the other end, he noted that high-risk patients are already recommended to start a statin regardless of what a scan shows, so ordering one ‘is likely to result in unnecessary testing.’
The CAC score itself runs from 0 to 1,000 or higher. As STAT News reported, risk climbs through stages: a score of 0 indicates no detectable calcified plaque, below 100 is considered mild, up to 300 is moderate, and above 300 is classified as severe. In principle, that granularity should add diagnostic value. The Northwestern study suggests it does, but mainly for the patients for whom the initial PREVENT estimate was least decisive.
Clinical guidelines have already moved in this direction. The 2026 American College of Cardiology and American Heart Association multisociety guideline on dyslipidaemia management, as Medscape reported, recommended selective use of CAC scoring specifically in adults with borderline or intermediate 10-year cardiovascular risk when the decision about lipid-lowering therapy remains uncertain. The new study’s findings align with that position, and Shah said the results also support the clinical usefulness of the PREVENT calculator itself. Even without calcium data, PREVENT performed well at predicting cardiovascular risk.
The study was published on 26 August in JAMA under the title ‘Predictive Utility of Coronary Artery Calcium Score Added to the PREVENT Atherosclerotic Cardiovascular Disease Equations.’ It was supported by the American Heart Association and the National Heart, Lung, and Blood Institute.
Gaps remain. The researchers said further work is needed to establish how much calcium scores improve PREVENT estimates in higher-risk groups, specifically South Asian and Filipino adults, as Shah noted. The age range of 45 to 79 also means the findings do not extend to younger adults, and separate studies will be needed there. Shah and his team have set out clearly who is and is not likely to gain from the scan; determining whether those conclusions hold across more diverse and younger populations is the next question.
