Calcium Score: What To Know About Coronary Artery Calcium Testing

Your blood work is in, and your low-density lipoprotein (LDL), or "bad," cholesterol remains stubbornly high. But your overall risk of heart disease is neither high nor low. Now what? 

A heart computed tomography (CT) scan, also called coronary artery calcium (CAC) test, and calcium score might provide the necessary information you and a healthcare provider need to decide the next steps.

Here's what you should know about CAC testing and calcium scores can help predict your risk of heart disease and heart attack, as well as risks of CAC testing and whether health insurance providers cover the costs.

What Is a Coronary Artery Calcium (CAC) Test?

The American College of Cardiology (ACC) and American Heart Association (AHA) included the CAC test in cholesterol management guidelines published in November 2018. The screening test results can predict your risk of a heart attack.

The scan can also help differentiate people at moderate risk for heart disease into high- or low-risk groups, Mary Norine Walsh, MD, former president of the ACC and medical director of heart failure and cardiac transplantation at St. Vincent Heart Center of Indiana, told Health.

"That piece of information alone can't help prevent a heart attack or stroke," said Dr. Walsh. But the action people take on those results can make a difference.

Still, the test isn't universally endorsed. In July 2018, the U.S. Preventive Services Task Force (USPSTF) said that evidence was "insufficient" to weigh the benefits and harms of adding the test to risk assessment measures for heart attack and stroke prevention in people without symptoms.

The test itself is painless and takes around 15 minutes. A CT scan, a type of low-dose X-ray of your coronary arteries, shows "calcified" or hardened plaque that may be present. Your coronary arteries are the blood vessels that supply blood to your heart muscle. Then, healthcare providers measure and score the amount of calcified plaque.

What Is Calcium Scoring?

Based on the scan results, you'll receive a calcium score. The score ranges from zero to more than 400. Here's what those numbers mean:

• 0: No plaque is present, and your risk of heart attack is low.
• 1 to 10: A small amount of plaque is present. You have a 10% chance of heart disease, and your risk of heart attack is low.
• 11 to 100: Some plaque is present. You have mild heart disease and a moderate chance of heart attack.
• 101 to 400: A moderate amount of plaque is present. You have heart disease, and plaque may be blocking an artery. Your chance of having a heart attack is moderate to high.
• More than 400: A large amount of plaque is present. There's more than a 90% chance that plaque is blocking one of your arteries, and your chance of a heart attack is high.

The scale itself has no upper end, Ron Blankstein, MD, former president of the Society of Cardiovascular Computed Tomography and a preventive cardiology specialist at Brigham and Women's Hospital, told Health. In some cases, people may have scores greater than 1,000, said Dr. Blankstein.

Who Should Have a Coronary Calcium Test?

A CAC test doesn't replace traditional risk assessment tools that factor in LDL cholesterol, blood pressure, and smoking. According to the Centers for Disease Control and Prevention (CDC), nearly half of adults in the United States have at least one of those risk factors.

Still, a CAC test can help you and a healthcare provider decide whether your risk for heart attack is high enough to consider cholesterol-lowering therapy. That therapy may include medications like statins. 

But if your risk is neither high nor low, it may be a tough call. After all, why start a statin if your arteries are clean as a whistle? In that case, a healthcare provider may use a personalized approach that considers your risk factors and calcium scores.

Why Is LDL Cholesterol Important?

High LDL cholesterol, 160–189 milligrams per deciliter, is one of the significant risk factors for heart disease. An LDL cholesterol level of less than 70 milligrams per deciliter is optimal for people with a high risk for heart disease. For everyone else, the goal is less than 100 milligrams per deciliter.

Under the 2018 AHA and ACC guidelines, calcium scoring may be an option for adults aged 40–75 without diabetes if their LDL cholesterol is 70 milligrams per deciliter or higher. But their heart attack or stroke risk over the next 10 years is "uncertain." 

Also, calcium scoring may be helpful if their LDL cholesterol is between 70–189 milligrams per deciliter and their 10-year heart disease risk is "intermediate." But a decision about starting treatment is uncertain.

"It's definitely something we want to use when our risk is kind of in the range where maybe we want to start a statin, maybe we don't," Anthony Pearson, MD, a preventive cardiology specialist at Saint Louis University, told Health.

What Are the Benefits of CAC Testing?

If your calcium score is zero, your heart disease risk is lower than predicted by other tests. So, you might be able to avoid or delay statin therapy if you don't smoke, have diabetes, or have a family history of heart disease.

In fact, a study published in 2018 in the Journal of the American College of Cardiology looked at more than 13,600 people over 10 years. The researchers found no clinical benefit of starting statins in people with a calcium score of zero.

But for people younger than 65 with a score greater than 100, "you're going to benefit a lot" from starting a statin, said Dr. Pearson. Evidence of plaque could even kick-start lifestyle changes to prevent heart disease. 

"For example, someone who's smoking may be more motivated to quit," added Dr. Walsh.

What Are the Risks of CAC Testing?

There are several risks associated with CAC testing, which include:

• Radiation exposure: Every time you have a CT scan, you expose yourself to radiation. The dose of radiation is relatively low. Still, exposure may be concerning if you require repeated scans. 
• Mental health effects: For others, reclassified into a high-risk category could pose "psychological harm," per the USPSTF. 
• False comfort: Young adults with a score of zero can still have a significant build-up of non-calcified plaque. For that reason, people should still make healthy lifestyle choices.
• Misleading results: It's possible to get a high calcium score even if your arteries show no signs of heart disease. False results are most likely to occur among people with a low risk for heart disease.

Plus, there's a chance the scan will reveal "incidental findings," extra things that appear on the test, like a nodule on your lung. Depending on their nature, incidental findings may require follow-up scans and procedures.

Should I Have a CAC Test?

Healthcare providers previously considered calcium scoring unnecessary for young adults aged 20–30. Calcified plaque is unusual in that low-risk age group. But one study published in 2017 in JAMA Cardiology indicated that a nonzero CAC score of any level in young adults indicates a much higher risk of heart attack and death than in other age groups.

For people aged 20–39, embracing a heart-healthy lifestyle can help decrease the risk of heart disease and heart attack, including:

• Eating a healthy diet
• Regularly exercising
• Quitting smoking 
• Controlling stress
• Maintaining a healthy body weight
• Managing any health conditions, like diabetes
• Limiting alcohol
• Getting plenty of sleep

A CAC test may also not be suitable for high-risk patients. For people in that group, guidelines call for statins and other preventive treatments, such as lifestyle changes, to mitigate heart-related complications.

Talk to a healthcare provider about your heart disease risk. You can also estimate your risk using an online calculator, such as those offered by the ACC and the National Heart, Lung, and Blood Institute (NHLBI).

"Knowing your risk factors is the important first step," said Dr. Walsh.

CAC Testing Costs

If you decide to get a CAC test, you'll likely pay out of pocket, and the price is generally $100 to $400. But self-pay rates vary widely across the United States.

As to why insurers in most states don't cover the test, as of January 2023, there's a lack of high-quality data showing that CAC testing reduces the rate of heart-related complications, including heart attacks. But some observational evidence suggests that calcium scoring can help identify people who may benefit from preventive therapies. 

But you may be in luck if you live in Texas. As of June 2022, Texas is one of the only states with laws ensuring insurance coverage for CAC tests for eligible patients.

Ultimately, many healthcare providers specializing in preventive cardiology utilize CAC testing and calcium scoring in people and would like to see it reimbursed. 

So, until insurers decide to cover the test, keep managing your risk factors for heart disease. Talk to a healthcare provider if you think this test would benefit you.

A Quick Review

CAC testing helps healthcare providers assign you a calcium score, which may predict your heart disease risk. Also, your calcium score may indicate whether preventative therapies, like statins and lifestyle changes, will help mitigate heart-related complications.

Still, CAC testing does not replace standard testing for heart disease, like a lipoprotein panel (lipid panel), which measures your cholesterol. Overall, consult a healthcare provider about your heart disease risk and what tests are right for you.