Coronary Calcium Scans: Who Really Needs Them?

Coronary artery calcium scans have become a widely used tool for evaluating an individual’s future risk of heart disease. This quick, relatively inexpensive CT test measures the buildup of calcium in the coronary arteries, which supply blood to the heart. However, new research from Northwestern Medicine suggests that the scan’s greatest benefits may be limited to a more specific group of patients than previously thought.

In a study tracking over 6,000 adults for a decade, researchers found that adding a coronary artery calcium score to the American Heart Association’s primary cardiovascular risk calculator, known as PREVENT, yielded only marginal improvements in risk prediction for the general population.

How Heart Calcium Scans Measure Risk

PREVENT estimates a person’s likelihood of developing cardiovascular disease over the next 10 or 30 years using standard health metrics, such as blood pressure, cholesterol levels, age, and sex.

In contrast, a coronary artery calcium scan directly images the coronary arteries to detect calcium-containing plaque. The resulting calcium score reflects the amount of visible calcified plaque, with higher scores generally indicating a greater risk of future cardiovascular events.

The new findings suggest that calcium scores become particularly useful when PREVENT initially classifies a patient as having borderline or intermediate risk. Within this specific cohort, the scan provides a clearer distinction of who is more likely to experience cardiovascular disease and who is not.

“Coronary artery calcium scans are becoming more widely available and less expensive,” said study senior author Dr. Nilay Shah, assistant professor of medicine in the division of cardiology at Northwestern University Feinberg School of Medicine. “Our findings suggest that not everyone necessarily needs or would benefit from a coronary artery calcium scan for the purpose of predicting the risk of heart attack and stroke.”

Shah noted that the findings also highlight potential drawbacks of using scans in situations where they are unlikely to alter clinical management.

“Routinely using calcium scans in low-risk individuals may lead to unnecessary radiation exposure, additional testing, and costs without clear clinical benefits,” Shah added. “Conversely, using scans in high-risk individuals is likely to result in unnecessary testing, as these patients are already recommended to start statin therapy regardless of the scan results.”

The study was published on Aug. 26 in JAMA.

Comparing Predictions With Real Outcomes

To evaluate the incremental value of calcium scans, Shah and his colleagues analyzed data from more than 6,000 adults aged 45 to 79 who participated in the Multi-Ethnic Study of Atherosclerosis.

At the start of the study, each participant underwent both a coronary artery calcium scan and received a PREVENT estimate of their risk of a cardiovascular event within the next 10 years.

Researchers then tracked the participants’ actual health outcomes over the following decade.

During the 10-year follow-up, 6% of the participants experienced a heart attack or stroke. When the researchers compared predictions incorporating calcium scores with those based on PREVENT alone, the overall improvement in predictive ability was modest.

The model’s discrimination, a metric measuring how effectively it distinguishes between individuals who will and will not experience a cardiovascular event, increased only slightly from 0.73 with PREVENT to 0.75 when calcium scores were included.

However, the results changed significantly when the analysis focused on individuals whose initial PREVENT scores placed them in the borderline or intermediate risk categories—specifically, those with an estimated 3% to 9% risk of cardiovascular disease within 10 years.

For this intermediate-risk group, incorporating the calcium score led to a more meaningful improvement in predicting future cardiovascular events.

“For patients at borderline risk, knowing their calcium score can help clarify whether their actual risk is lower or higher than initially estimated, which can directly guide treatment decisions,” Shah explained.

Finding the Patients Most Likely to Benefit

Cardiovascular disease remains the leading cause of death in the United States, affecting approximately 10% of adults aged 30 to 79. Yet, many heart attacks and strokes are preventable, Shah emphasized.

Accurately identifying an individual’s risk is crucial for determining who is most likely to benefit from preventive treatments, such as statins, which lower cholesterol and reduce cardiovascular risk.

“The findings help us understand how best to use our existing tools to estimate the risk of a heart attack or stroke. This provides more precise guidance on who is most likely to benefit from statin therapy to prevent heart disease,” Shah said.

Shah added that the results also support the clinical utility of the relatively new PREVENT calculator, which performed well in predicting cardiovascular risk even without the addition of calcium scan results.

Questions That Still Need Answers

The researchers emphasized that additional studies are needed to determine how much calcium scores can improve PREVENT estimates in specific populations.

This includes higher-risk groups, such as South Asian and Filipino adults, Shah noted. Furthermore, more research is required in younger populations, as the participants in this study were between the ages of 45 and 79 at the onset of the research.

Other Northwestern co-authors are Xiaoning Huang, Lucia Petito, Norrina Allen, Dr. Philip Greenland, and Dr. Sadiya Khan.

The study is titled, “Predictive Utility of Coronary Artery Calcium Added to the PREVENT Atherosclerotic Cardiovascular Disease Equations.” It was supported by the American Heart Association (grant 24CDA1266732) and the National Heart, Lung, and Blood Institute (contracts 75N92020D00001, HHSN268201500003I, N01-HC-95159, 75N92020D00005, N01-HC-95160, 75N92020D00002, N01-HC-95161, 75N92020D00003, N01-HC-95162, 75N92020D00006, N01-HC-95163, 75N92020D00004, N01-HC-95164, 75N92020D00007, N01-HC-95165, 75N92020D00001, N01-HC-95166, 75N92020D00002, N01-HC-95167, 75N92020D00003, N01-HC-95168, 75N92020D00004, N01-HC-95169, and grant K23HL157766).

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