IPM Take
Cardiovascular screening has an uncomfortable tendency to equate more information with better medicine.
This study suggests otherwise.
Among 6,098 adults without established atherosclerotic cardiovascular disease, adding a coronary artery calcium, or CAC, score to the American Heart Association’s PREVENT equations improved overall discrimination only modestly, from a C statistic of 0.73 by about 0.02. The additional scan became considerably more informative when researchers focused on patients whose baseline risk was neither clearly low nor clearly high.
Among people initially classified as borderline risk, actual 10-year ASCVD event rates ranged from just 1.9% among those with CAC 0 to 14.3% among those with CAC of at least 300. The same starting risk estimate was therefore hiding radically different levels of underlying coronary disease.
That is where precision prevention should focus.
The question is not whether CAC predicts cardiovascular disease. It clearly does. The question is whether ordering the scan changes a decision.
Executive Summary
The JAMA study analysed 6,098 adults aged 45 to 79 years from the Multi-Ethnic Study of Atherosclerosis who had no ASCVD at baseline. Mean age was 61.4 years, 52% were women, and almost half, 49%, had detectable coronary calcium. Over 10 years, 366 participants, or 6%, experienced an ASCVD event.
Researchers compared risk prediction using the PREVENT-ASCVD equations alone with prediction after adding CAC scores. PREVENT incorporates routinely available clinical factors and categorises 10-year risk as low below 3%, borderline from 3% to below 5%, intermediate from 5% to below 10%, and high at 10% or above.
Across the overall cohort, adding CAC produced only a modest improvement in model discrimination and reclassification. The benefit was concentrated among those in borderline and intermediate risk categories.
In the borderline-risk group, observed 10-year ASCVD event rates were:
- 1.9% with CAC 0
- 3.9% with CAC 1 to 99
- 7.4% with CAC 100 to 299
- 14.3% with CAC 300 or higher.
These findings closely align with the 2026 US dyslipidaemia guideline, which recommends selective CAC testing in intermediate-risk and selected borderline-risk adults when the decision about lipid-lowering therapy remains uncertain, rather than routine scanning across all risk groups.
Why it matters
- HTA bodies: The study is a useful reminder that diagnostic value depends on clinical context. A test can predict disease accurately yet offer limited incremental value if the treatment decision was already clear before it was ordered. Evaluation should focus on reclassification and decision impact, not prognostic association alone.
- Payers: Selective CAC use offers a potential route to higher-value imaging. Funding scans where they can realistically alter statin initiation or intensity is more defensible than broad screening of low-risk patients or routine confirmation of already high-risk patients.
- Industry / innovation partners: As imaging, biomarkers and AI risk tools proliferate, the competitive standard will increasingly be incremental clinical utility. New diagnostics will need to show that they change treatment decisions or outcomes beyond inexpensive existing risk models, not simply produce another risk score.
Coronary artery calcium scanning has an intuitive appeal.
A conventional risk calculator estimates the probability that cardiovascular disease will emerge. A CAC scan can show that coronary atherosclerosis is already present.
That distinction makes the test one of preventive cardiology’s most powerful tools, but also creates a temptation to scan broadly.
The new JAMA analysis suggests that would miss the point.
Researchers applied the PREVENT-ASCVD equations to more than 6,000 adults and then examined how much prediction improved once their CAC scores were added. Across everyone combined, the gain was modest.
That makes sense at the extremes.
Someone with very low estimated risk is unlikely to need aggressive lipid-lowering treatment regardless of a scan, while someone already at clearly high risk may warrant treatment whether calcium is visualised or not. Imaging can add information without adding much decision value.
The uncertain middle is different.
One risk category can hide very different disease
The most striking findings came from people classified as borderline risk by PREVENT.
A person in this group with CAC 0 had a 1.9% observed event rate over 10 years. Another person with the same initial risk category but CAC of at least 300 had a 14.3% event rate.
That is not a small refinement.
One result may support postponing pharmacological treatment in an appropriately selected patient, while the other may strengthen the case for lipid-lowering therapy and more intensive prevention.
This is precisely how CAC is positioned in the 2026 ACC/AHA multisociety dyslipidaemia guideline. PREVENT should be used first, and CAC is recommended selectively when a patient falls into the borderline or intermediate range and uncertainty remains after the clinician-patient discussion.
For selected patients with CAC 0, treatment can sometimes be deferred when other major high-risk conditions are absent. At the opposite end, a CAC score above zero, particularly at least 100 or above the 75th percentile, strengthens the case for lipid-lowering therapy.
The principle is broader than coronary calcium.
The best diagnostic test is not necessarily the one that detects the most disease. It is the one that resolves a meaningful clinical uncertainty.
More imaging is not automatically more precise medicine
CAC scanning is relatively quick and inexpensive, but it still involves radiation, cost and the possibility of downstream testing after incidental or unexpected findings.
Those trade-offs become harder to justify when the result is unlikely to change management.
The JAMA study therefore offers an important counterweight to a technology-driven model of precision medicine in which increasingly detailed information is assumed to be inherently valuable.
Precision can also mean knowing when not to test.
There are limitations. The analysis was observational, and all participants were aged 45 to 79, so the findings cannot define the role of CAC in younger adults. The authors also note uncertainty in some populations, including South Asian and Filipino adults, whose risk may not be fully represented in the cohort.
The study also does not show directly that CAC-guided decisions reduce cardiovascular events compared with PREVENT-guided care alone.
What it does provide is a clearer answer to a practical question increasingly faced by clinicians and health systems.
A coronary calcium scan is not equally useful for everyone.
Its greatest value may lie exactly where precision medicine should operate: where the next piece of information has a realistic chance of changing what happens to the patient.
