Calcium Score Screening Test

What is a Calcium Score?

A calcium score refers to a screening test that is used to calculate the amount of calcium in the heart.  A calcium score looks specifically at calcium in the coronary arteries, where increased calcium leads to narrowing of the artery.  This is important because the narrowing in the artery (known as steonsis) may result in a heart attack.

How is a Calcium Score Calculated?

The calcium score is calculated from Computed Tomography (CT) scan images.  The two main types of CT scanners are "Electron Beam" (EBCT) and "Multi-Detector" (MDCT).  Both types of scanners are generally effective in calculating a calcium score. 

Areas of calcium appear "brighter" on the CT scan, and a computer is able to quantify the amount of calcium based on the size of these areas.  The amount of calcium calculated is reported as a number.  The calcium score may be completed as a separate test, or in combination with a study to look specifically at the arteries (CT-Angiogram).

What is the Purpose of a Calcium Score?

The purpose of a calcium score is to determine if a patient is at high risk for coronary artery disease, which may lead to a heart attack.  In general, a high calcium score is associated with a higher risk of cardiovascular events, while a calcium score of zero is associated with a very low risk of coronary artery disease or heart attack.

A calcium score is considered a "screening" test.  The main screening test used by physicians to determine if coronary artery disease is present is known as the Framingham Risk Score.  This test looks at age, gender, blood pressure, smoking history, and cholesterol levels to determine who is at risk for a heart attack.  This risk score is then used by physicians to determine which patients should be treated with cholesterol medications.  The Framingham Risk Score (FRS) has been proven by studies to predict which patients will benefit from cholesterol lowering medications.

Unfortunately, the Framingham Risk Score is not perfect, and some people may have a heart attack even with low risk score.  Calcium scores are not currently recommended as a screening tool by the major heart associations, but they provide additional information that may be helpful in certain situations.  For example, a patient may be calculated to have a low Framingham Risk Score, but actually have high calcium score.  This patient may benefit from more aggressive control of cholesterol with medical therapy.  In general, the FRS is a proven screening test, and it is not known if treating patients with high calcium score leads to better outcomes.  Therefore, a calcium score is probably best used for patients with a moderate risk calculated by FRS.  If the calcium score is high, the patient may benefit from more aggressive therapies.

Calcium Score Results - What do they mean?

Prior studies have used cutoff values to determine high and low calcium scores.  One study defined a low calcium score as < 100, and high as > 400 (Reference). 

It is important to note that calcification of the coronary arteries is part of the aging process, and all people develop calcium with age.  For example, one study looked at calcium scores and coronary arteries using angiography.  Almost all patients (95%) less than 40 years old with calcium score of less than 8 had no significant narrowing of the arteries.  In patients over 70 years old, this number was much higher.  Almost all patients in the elderly group with a calcium score less than 134 had no narrowing of the arteries (Reference).  This study shows that the calcium score must be interpreted in relation to the age, gender, and medical conditions of each patient.

What is the Downside to a Calcium Score?

Many patients are tempted to get a calcium score based on advertisements, but there are risks to a calcium score test.  First, there is a risk with all CT scans associated with radiation exposure.  A calcium score uses relatively little radiation, but the radiation dose may be considerable if combined with a CT-Angiogram.  Secondly, there has not been any large study proving that patients treated based on calcium scores have better outcomes.  A calcium score may also lead to unnecessary procedures that also have risks.  For example, a patient with a moderately elevated calcium score and no symptoms may be referred for an invasive procedure.

Finally, there are "plaques" in the coronary arteries that do not have any calcium.  These are known as "vulnerable plaques" because they are more likely to lead to a heart attack than calcified plaques.  A calcium score will not identify the vulnerable plaque, and a patient may have a heart attack from a vulnerable plaque even with a low calcium score.

Should I get a Calcium Score?

In general, you should speak with your physician before getting a calcium score.  There are risks associated with calcium scores, and the study is unlikely to be helpful unless you are working closely with a physician who can help guide therapy.  Calcium scores are not currently recommended by major associations as a screening test, but there are cases where a calcium score may be beneficial.  The risks and benefits should be determined in a discussion with your physician.

Calcium Score Images

More Information

    • Computed Tomography Information at Medline Plus
    • Heart Scan Article at MSNBC