According to a study published on Aug. 26 in JAMA by Northwestern Medicine researchers, routine coronary artery calcium scans offer only modest overall predictive value beyond standard cardiovascular risk calculators. While the fast CT tests effectively identify calcified plaque, researchers found their greatest clinical benefit is restricted to patients categorized as borderline or intermediate risk.
How Coronary Artery Calcium Scans Measure Plaque Buildup
Coronary artery calcium scans use a quick, relatively inexpensive computed tomography test to measure calcium-containing plaque inside the arteries supplying blood to the heart. According to researchers, the resulting score reflects the amount of detectable calcified plaque. Generally, a higher score signals a greater risk of future cardiovascular disease. This imaging approach differs significantly from standard health metrics that rely purely on mathematical estimation.
By contrast, the American Heart Association’s primary cardiovascular risk calculator, known as PREVENT, estimates a person’s 10- or 30-year chance of developing cardiovascular disease. PREVENT uses commonly available health information like blood pressure, cholesterol, age, and sex, requiring no medical imaging.
Comparing Predictions With Real Outcomes Over a Decade
To evaluate how much extra predictive power scans provide, study senior author Dr. Nilay Shah and his colleagues examined data from more than 6,000 adults aged 45 to 79 participating in the Multi-Ethnic Study of Atherosclerosis, as detailed in the JAMA findings. At the start of the study, each participant received a calcium score alongside a PREVENT risk estimate.
Researchers tracked participants for 10 years, during which 6% of the group experienced a heart attack or stroke. When the team compared predictions mixing calcium scores with PREVENT estimates against PREVENT alone, the overall improvement proved modest. The model’s discrimination—which measures how well it distinguishes between individuals who will and will not experience a cardiovascular event—rose just slightly from 0.73 to 0.75.
Did You Know?
Cardiovascular disease remains the leading cause of death in the United States, affecting about 10% of U.S. adults aged 30 to 79.
Finding Patients Most Likely to Benefit From CT Testing
The predictive picture changed dramatically when researchers isolated participants whose initial PREVENT scores placed them in borderline or intermediate risk categories, meaning an estimated 3% to 9% risk of heart disease over 10 years. For this specific patient subset, adding the calcium score produced a meaningful improvement in forecasting future cardiovascular events.
“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 Dr. Nilay Shah, assistant professor of medicine in the division of cardiology at Northwestern University Feinberg School of Medicine.
Shah noted that routine scans for low-risk individuals can trigger unnecessary radiation exposure, testing, and costs with unclear clinical benefits. Conversely, scanning high-risk individuals is likely redundant because those patients are already recommended to start a statin regardless of scan outcomes.
Frequently Asked Questions
What does a coronary artery calcium score measure?
The CT test detects calcified plaque inside the coronary arteries, yielding a score where higher numbers indicate a greater burden of atherosclerosis and elevated future risk.
Who benefits the most from a heart calcium scan?
According to the Northwestern Medicine study, patients whose initial PREVENT risk calculator scores place them in the borderline or intermediate category (3% to 9% risk) gain the most precise risk clarification.
What are the drawbacks of routine scanning for low-risk patients?
Dr. Nilay Shah warns that scanning low-risk individuals can cause unnecessary radiation exposure, additional testing, and extra costs without clear clinical benefits.
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