Coronary Artery Calcium Test (CAC)

You've got a patient in the borderline-to-intermediate risk zone, and the statin conversation could go either way. A coronary artery calcium test is the tiebreaker that turns "maybe" into a clear decision you and the patient can both stand behind.

What is a CAC test?

It's a noninvasive, low-dose, non-contrast CT that measures calcified plaque in the coronary arteries and reports a calcium score.

• Higher scores mean higher future risk of MI and stroke.
• It doesn't see soft (non-calcified) plaque, so a low score doesn't fully exclude CAD. Even so, CAC is a strong predictor of events.

Why consider it?

• It helps with ASCVD prevention decisions, like starting a statin or, selectively, low-dose aspirin.
• It improves risk communication and adherence by showing patients their arterial calcium number.

Who should get a CAC test?

Usually appropriate (a shared decision):

• Age 40 to 75 with a 5 to 20% 10-year ASCVD risk (borderline to intermediate) when the statin decision is uncertain.
• Patients with multiple risk enhancers (HTN, smoking, low HDL, CKD, strong family history of premature ASCVD) when a result would change management.

Generally not appropriate:

• Known CAD (prior MI, stent, CABG) or active chest pain. Use diagnostic pathways, not CAC.
• Very low risk adults.
• Under 40 years unless there's a compelling history or risk.
• Situations where the result won't change therapy, for example LDL greater than or equal to 190 or diabetes age 40 to 75, where statins are indicated regardless.

Cost and radiation: typically $100 to $500 (often around $150). Radiation is roughly 1 mSv, which is low.

How to read the score

For aspirin in primary prevention, consider it only case-by-case in age 40 to 59 with a 10% or higher 10-year risk and low bleeding risk. Generally avoid starting aspirin at age 60 or older for primary prevention.

How often to repeat?

Only if the result would change management. Intervals sometimes used:

• Low risk (under 5%): 5 to 7 years
• Borderline or intermediate (5 to 10%): 3 to 5 years
• Diabetes: around 3 years

If therapy is already clearly indicated and the patient has accepted it, there's no need to repeat.

What to do with the result

All scores:

• Lifestyle: heart-healthy diet, exercise, smoking cessation, healthy BMI.
• BP optimization and sleep. Consider lipoprotein(a) or other risk enhancers if decisions are still uncertain.

Medication decisions:

• Statin: base it on the score plus overall risk (see the table).
• Aspirin: selective primary prevention only (see the note above).
• Consider cardiology referral for CAC 400 or higher, atypical symptoms, or complex risk.

Patient counseling script you can paste

"A CAC scan is a quick, non-contrast CT that shows calcium in the heart arteries. A score of 0 means very low risk over the next 5 to 10 years, and higher scores mean higher risk. We'll use your number to decide whether a statin, and rarely aspirin, will help you avoid a heart attack or stroke. No matter the number, lifestyle (food, movement, sleep, and not smoking) still matters most."

Frequently asked questions

If the CAC score is 0, does that rule out heart disease?
No. CAC doesn't see soft, non-calcified plaque, so a 0 doesn't fully exclude CAD. It does mean very low short-term event risk, which is why it can support deferring a statin in the right patient.

Should I order a CAC test if a statin is already clearly indicated?
No. If the patient has LDL greater than or equal to 190, diabetes in the 40 to 75 range, or known CAD, statins are indicated regardless, so the scan won't change the plan.

When is the score high enough to involve cardiology?
A CAC of 400 or higher, atypical symptoms, or complex risk are reasonable reasons to refer, along with high-intensity statin and aggressive risk-factor control.

A CAC test earns its place when it actually changes what you do next, mostly the statin decision in a borderline patient. For a one-page version of the score thresholds, the Clinical Desk Reference keeps it handy, and the Primary Care Clinical Mastery Program covers ASCVD prevention end to end. For the basics that lead up to this, see the hyperlipidemia overview and statin intolerance.

Education only. Use clinical judgment and your local guidelines.

Written by Allison Sowders, MSN, APRN, FNP-BC, a practicing primary care nurse practitioner and founder of Nurse Practitioner Mentor. Reviewed July 2026.