Patient Education
What Is a Coronary Calcium Score (CAC)? A Patient's Guide
A coronary artery calcium (CAC) score is one of the more practical tools in preventive cardiovascular medicine — but it's not for everyone. Here's an honest explanation of what the test is, who should consider it, and what the results mean.
What Is a CAC Scan?
A coronary artery calcium scan is a non-contrast CT scan of the heart. It takes approximately 10–15 minutes, involves no IV dye, and delivers a relatively low radiation dose. The scan detects and quantifies calcium deposits within the walls of the coronary arteries — the blood vessels that supply the heart muscle.
The result is expressed as an Agatston score — a number representing the total calcium burden measured across all coronary arteries. A score of 0 means no detectable calcium. Higher scores indicate progressively greater calcium burden.
Understanding the Agatston Score
| CAC Score | Interpretation |
|---|---|
| 0 | No calcium detected — lowest measurable short-term event risk |
| 1–99 | Mild calcium — increased risk compared to CAC 0 |
| 100–299 | Moderate calcium burden — significantly elevated risk |
| 300+ | Severe calcium — high cardiovascular event risk |
Score percentiles also matter: a 55-year-old with a score of 100 may be at the 75th percentile for their age/sex group, indicating higher relative risk than the score alone suggests. A cardiologist or provider interprets results in context.
Who Should Consider a CAC Scan?
Current ACC/AHA guidelines suggest CAC scoring in adults aged approximately 40–75 who are at intermediate cardiovascular risk (10-year ASCVD risk 7.5–20%) and where the result would change clinical management — such as the decision to start or withhold statin therapy.
CAC is generally not recommended for:
- Patients already on statins (results unlikely to change management)
- Very low risk patients (10-year ASCVD risk <5%)
- Very high risk patients (10-year ASCVD risk >20%) — already on treatment
- Patients with known coronary artery disease
What CAC Does Not Tell You
A CAC score of 0 is reassuring but does not eliminate cardiovascular risk. CAC only detects calcified plaque — it does not visualize soft (non-calcified) plaque, which can still cause heart attacks. If non-calcified plaque assessment is needed, a CCTA (coronary CT angiography) is the appropriate study.
Do You Need a Provider Order for a CAC Scan?
Yes — most imaging facilities require a provider order for CAC scanning. If you don't have a primary care doctor or your doctor hasn't ordered one, a telehealth provider consultation is an efficient option. Diagnostic Orders Direct provides a $40 virtual review to determine if a CAC order is medically appropriate for your situation.
Need a Provider Order for a CAC Scan?
Start Virtual Consult — $40Orders issued only when medically appropriate. Not affiliated with any imaging center.
Related Resources
- CAC Order Consultation Page
- CAC vs. CCTA: Which Is Right for You?
- Preventive Heart Scan Order Review
- Preventive Diagnostics Hub
This article is educational and does not constitute medical advice. Consult a licensed provider to determine if CAC scoring is appropriate for your individual situation.