Coronary artery calcium scans, a quick CT test that has grown popular with people worried about heart disease, added only a small improvement to standard risk estimates for most adults in a 10-year study of more than 6,000 people, Northwestern Medicine researchers reported in JAMA.
The scans made a bigger difference for one group: adults whose initial estimate fell in the borderline or intermediate range, defined in the study as a 3% to 9% estimated risk of cardiovascular disease within 10 years. For them, the calcium score helped clarify who was actually more or less likely to have an event.
That distinction matters for everyday decisions about statins. Many middle-aged adults are weighing whether to start one, and some pay out of pocket for a scan without knowing whether the result will change their plan.
Where the Scan Changed the Picture
The researchers used data from the Multi-Ethnic Study of Atherosclerosis, which enrolled adults ages 45 to 79. At the start, each participant received a calcium score and an estimate from PREVENT, the American Heart Association's primary risk calculator, which uses routine information such as blood pressure, cholesterol, age, and sex.
Over the next decade, 6% of participants had a heart attack or stroke. Adding calcium scores to PREVENT only slightly improved the model's ability to separate people who had events from those who did not, raising a measure called discrimination from 0.73 to 0.75, according to a Northwestern University summary.
The improvement was larger in the borderline and intermediate group. "For patients at borderline risk, knowing their calcium score can help determine whether their risk is actually lower or higher than initially estimated, which can help guide treatment decisions," said senior author Dr. Nilay Shah, an assistant professor of medicine in the division of cardiology at Northwestern University Feinberg School of Medicine.
Shah said the results also support the relatively new PREVENT calculator, which performed well on its own.
The study, published Aug. 26 and recently highlighted by ScienceDaily, was supported by the American Heart Association and the National Heart, Lung, and Blood Institute.
Evidence Check on a Popular Test
This research addressed a narrow question: how much a calcium score adds to PREVENT. It did not test whether calcium buildup predicts heart disease, which earlier research has long supported, and it did not test whether scanning people leads to fewer heart attacks.
Shah cautioned against using the scan when it is unlikely to change care. "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. High-risk adults, he added, are already advised to start a statin regardless of what the scan shows.
The findings have limits. Participants were 45 to 79 when they enrolled, so the results may not apply to younger adults. The researchers said more study is needed in higher-risk groups, including South Asian and Filipino adults. The analysis was observational and relied on an established research cohort rather than a randomized trial.
STAT reported that this was one of two studies published in August that used the same cohort to examine calcium scores alongside PREVENT, and both found that the scan made a difference mainly when risk was borderline or intermediate. STAT also noted that current ACC and AHA guidelines recommend using calcium findings to inform statin decisions for some men 40 and older and women 45 and older at borderline or intermediate risk.
MedicalDaily Evidence Check: This was an observational analysis of more than 6,000 adults followed for 10 years and published in JAMA. It found that the scan added modest value overall and more value at borderline and intermediate risk. It did not show that scanning improves outcomes, and it does not replace a clinician's recommendation.
Deciding Whether to Get Scanned
The people most likely to benefit are adults whose PREVENT estimate lands in the 3% to 9% middle ground and who are unsure about starting a statin. People at low estimated risk may gain little, and people at high risk are generally advised to consider a statin either way.
Before booking a scan, ask a primary care clinician or cardiologist to calculate your PREVENT risk using recent blood pressure and cholesterol results. Ask how a calcium score would change your treatment plan. If it would not, the scan may not be worth the cost or the radiation.
Calcium scans are often marketed directly to consumers, and insurance coverage varies. Check with your insurer about costs before scheduling, and make sure a clinician will review the results with you.
A calcium score may shift a borderline patient's estimated risk lower or higher, which can tip a statin decision either way. The scan is one input, not a diagnosis. Mention any family history of early heart attacks, since that history can change how a clinician reads any estimate.
Do not stop or start a statin based on a scan result alone. Discuss the full picture, including family history, smoking, diabetes, and kidney disease, with a clinician.
A scan does not rule out an emergency, and symptoms always come first. Chest pain, shortness of breath, sudden weakness, or trouble speaking requires a 911 call. The American Heart Association lists heart attack and stroke warning signs.
The researchers say more studies are needed in younger and higher-risk populations. MedicalDaily will follow whether professional groups update guidance on when calcium scoring should be used.
Key Questions Answered
What is a coronary artery calcium scan? A CT scan that detects calcium-containing plaque in the heart's arteries and produces a calcium score.
What did the study find? For most adults, the score added only a small improvement to the PREVENT risk calculator. It helped more for people at borderline or intermediate risk.
What counts as borderline or intermediate risk? In this study, a PREVENT estimate of 3% to 9% risk of cardiovascular disease within 10 years.
Should everyone get a calcium scan? The researchers say not everyone needs one. Low-risk people may face unnecessary radiation, testing, and costs.
Does the study prove scans prevent heart attacks? No. It measured how much scores improve risk prediction, not whether scanning improves outcomes.
Does the result apply to younger adults? Participants were 45 to 79, so more research is needed in younger people.
What should I ask my doctor? Ask for your PREVENT estimate and whether a calcium score would change your treatment.
