People are increasingly looking to coronary artery calcium scans as a quick and painless way to learn more about their heart health risk—important information, considering heart disease is the leading cause of death in the United States. But as counterintuitive as it may seem, a recent study suggests that these scans aren’t worthwhile for everyone.

The new research found that people at borderline or intermediate risk of heart disease stand to benefit the most from CAC scans, compared with those at either high or low risk.1

Of course, every person is different, and it’s always worth consulting your primary care physician or cardiologist to determine which diagnostic tests are right for you. In the meantime, here’s what you need to know.

What Are CAC Scans?

CAC scans are non-contrast CT scans of the heart that doctors use to look for evidence of calcified plaque in the coronary arteries.2 The scans take only a few minutes and don’t require fasting or medications. That said, as CT scans, they do expose patients to a small amount of radiation.3

Doctors calculate calcium scores based on the volume and density of calcium within coronary arteries. Generally, the higher the score, the greater the risk of a heart attack.

According to Michael Wilkinson, MD, a cardiologist with UC San Diego Health, the scans can be a powerful tool for helping patients understand their heart health and potentially move forward with appropriate interventions. “There’s a big difference between seeing a number from a lipid panel and seeing calcified plaque in your arteries, and sometimes, that really goes a long way,” he said.

Why Did Researchers Want to Examine CAC Scans?

Patient interest in CAC scans has sharply increased over the years, in part because an increasing number of health centers now offer them without a prescription or physician order.4 But easier access has also raised concern among cardiologists that some people might be getting them unnecessarily. The tests might be simple, but they still involve radiation.

That unease prompted Nilay S. Shah, MD, MPH, an assistant professor of cardiology at Northwestern University Feinberg School of Medicine, to conduct the new study.

“The idea and the motivation for the research was to better understand who best would benefit from getting the information from a calcium scan, and how should we most appropriately be using them,” Shah said.

Shah and his team specifically wanted to know whether adding calcium scoring to the American Heart Association-recommended PREVENT equation to calculate 10-year risk for atherosclerotic cardiovascular disease (ASCVD) would improve the model’s performance. PREVENT scores consider factors such as blood pressure, age, and cholesterol to estimate a person’s 10- and 30-year risk of developing heart disease, including atherosclerotic cardiovascular disease and heart failure.5

For high-risk patients, Shah said the next step is often clear: taking a statin to lower cholesterol. But for people at borderline risk, deciding whether to take action can be less straightforward based on the score alone.

The new study “is an example of people trying to get into the nuances of how these risk scores will perform if you add things like imaging,” said Eugene Yang, MD, MS, FACC, a cardiologist and professor of cardiology and medicine at the University of Washington School of Medicine, who was not involved with the study.

How Did the Study Work, and What Did It Find?

To test how effectively calcium scoring can complement PREVENT-ASCVD scores in predicting cardiovascular risk, Shah’s team used data from the Multi-Ethnic Study of Atherosclerosis, a long-term research project sponsored by the National Heart, Lung, and Blood Institute that’s tracked the coronary health of more than 6,800 male and female participants from various racial backgrounds since 2000.

The researchers worked in two stages. During the first phase, they used the PREVENT-ASCVD equations to divide participants into low, borderline, intermediate, and high-risk categories. Then, they added participants’ calcium scores to the model to see if that yielded more accurate predictions than just the PREVENT-ASCVD equations alone.

In this case, adding calcium scores didn’t make much difference. But then in the second phase, the team zoomed in on participants with borderline and intermediate risk. This time, Shah said, “we had a much more substantial reclassification.”

In other words, the researchers found that calcium scans did little to enhance predictions for participants at high and low risk, but it provided valuable information for those with borderline to intermediate risk.

As all three experts pointed out, a central limitation of this study is that it followed one particular group of people, which means it may not fully represent all groups. For that reason, Wilkinson said, “It’ll be important to see something like this replicated in other cohorts.”

Since the research project began more than 20 years ago, Shah added, the health of the general population has changed, so the findings may not reflect today’s population. However, the tradeoff was that researchers were able to examine outcomes over a long period of time.

What This Means For You

Whatever your estimated risk or intervention you’re considering, it’s crucial to speak with your doctor. Guidelines and research can provide a framework for care, Shah said, “but it’s really important that every patient and their clinician has a risk-benefit discussion for shared decision-making.”

That said, Shah recommends CAC testing for people at borderline or intermediate risk—meaning their estimated 10-year risk falls between 3% and 10%—echoing guidance from the American Heart Association.2When those patients are unsure about taking a statin, he said, “A calcium score would be useful because it kind of breaks the tie.”

Wilkinson, however, thinks people on the cusp shouldn’t necessarily rule themselves out. “I think for even those patients who fall maybe a little bit outside of those 10-year risk estimates, using calcium scoring to personalize their risk assessment can be very helpful,” Wilkinson said.

Keep in mind that even eligible patients may not have their CAC scan covered by insurance. According to the American Heart Association, the test usually costs $50 to $250 without insurance.3

It’s also important to discuss your results with a qualified clinician—even if you got the scan without a prescription. This is especially important if the results are abnormal, Yang said, as patients “really need to make sure that they have somebody that can appropriately follow up with them.”