CT Calcium Score for Coronary Artery Disease Risk Assessment
A CT calcium score is recommended for asymptomatic adults aged 40-75 years with borderline to intermediate risk of coronary artery disease (CAD) to guide decision-making about preventive interventions. 1
Indications for CT Calcium Scoring
Primary Indications
- Intermediate risk patients: 7.5% to <20% 10-year atherosclerotic cardiovascular disease (ASCVD) risk 1
- Borderline risk patients: 5% to <7.5% 10-year ASCVD risk 1
- Selected low-risk patients: Particularly those with family history of premature CAD 1
Specific Populations That Benefit
- Adults aged 40-75 years without known CAD 1
- Patients where decisions about preventive interventions (such as statin therapy) are uncertain 1
- Patients where risk reclassification would change management 2
Risk Stratification Based on Calcium Score
| CAC Score | Risk Category | Management Recommendation |
|---|---|---|
| 0 | Low risk | Consider withholding statins unless other risk factors present |
| 1-99 | Intermediate risk | Consider moderate-intensity statin, especially in those over 55 |
| ≥100 | High risk | Initiate statin therapy regardless of lipid levels |
| >400 | Very high risk | High-intensity statin therapy + consider additional screening for ischemia |
Clinical Value of Calcium Score
- Zero score: Extremely low risk of future cardiovascular events - no patients with CAC=0 had events in follow-up studies 3
- Score ≥100: Associated with significantly higher all-cause and cardiovascular mortality 4
- Reclassification power: CAC score ≥100 reclassifies patients to a higher risk category, with event rates similar to those seen in secondary prevention populations 2
- Location matters: Left main coronary artery calcification carries higher risk than other vessels 2
- Multi-vessel involvement: Risk increases with the number of calcified vessels 2
Important Caveats and Limitations
- CAC score does not detect non-calcified atherosclerotic plaque 1
- In symptomatic patients, a CAC score of 0 does not exclude obstructive CAD (present in 7-38% of symptomatic patients with CAC=0) 1
- Do not down-classify risk in patients with CAC=0 who have:
- Persistent smoking
- Diabetes
- Family history of premature ASCVD
- Chronic inflammatory conditions 2
- CAC scoring is not recommended for:
Follow-up Recommendations
- Repeat scanning intervals based on risk level:
- Low-risk patients: 5-7 years
- Borderline to intermediate-risk patients: 3-5 years
- High-risk patients or those with diabetes: 3 years 2
- Progression of CAC >15% per year is associated with a 17-fold increased risk for incident CHD events 2
Consensus Among Guidelines
The 2021 ACC/AHA guidelines, 2017 Society of Cardiovascular Computed Tomography expert consensus, and 2016 European guidelines all support the use of CAC scoring for risk stratification in intermediate-risk patients 1. The American College of Radiology appropriateness criteria also rate CAC scoring as "appropriate" for intermediate-risk patients 1.
By using CAC scoring appropriately in the indicated populations, clinicians can better identify patients who would benefit most from preventive therapies while avoiding unnecessary treatment in those at truly low risk.