When do you repeat a coronary artery calcium (CAC) score?

When to Repeat Coronary Artery Calcium (CAC) Score

For most patients with an initial CAC score of zero, repeat scanning should be performed in 5 years, while those with CAC scores between 1-400 warrant repeat testing in 3-5 years if results would change management decisions. 1, 2

Standard Rescanning Intervals by Initial CAC Score

CAC = 0 (Zero Calcium)

• Low-risk patients (<5% 10-year ASCVD risk): Repeat CAC in 5-7 years 2
• Borderline to intermediate-risk patients (5-19.9% 10-year risk): Repeat in 3-5 years 2
• General recommendation: Do not repeat sooner than 5 years from initial scan 1, 3
• Research demonstrates that 62% of patients with initial CAC = 0 remain at zero even after 5 years, and only 2% develop significant progression (>50 units) 3

CAC = 1-99 (Mild Disease)

• Repeat scoring in 3-5 years if results might change treatment decisions 2
• This interval applies when progression would support intensification of preventive management 2

CAC = 100-400 (Moderate Disease)

• Standard patients: Repeat at 3-5 years 2
• Diabetic patients: Repeat at 3 years 1, 2
• Patients with LDL-C ≥70 mg/dL: Repeat at 3 years to assess for accelerated progression (>20-25% per year) or increase to CAC >300 2

CAC >400 (Extensive Disease)

• Repeat CAC generally not required, as these patients are typically symptomatic and already receiving vigorous treatment 1, 2
• Functional testing may be indicated on an individualized basis rather than repeat calcium scoring 1

Clinical Scenarios Requiring Earlier Rescanning (3-5 Years)

High-Risk Clinical Features

Even with CAC = 0, consider repeat scanning in 3-5 years for patients with: 2

• Active cigarette smoking (CAC = 0 does not exclude noncalcified plaque risk)
• Diabetes mellitus
• Chronic inflammatory conditions (rheumatoid arthritis, psoriasis) where CAC = 0 does not exclude increased thrombotic risk
• Family history of premature ASCVD, particularly in younger patients
• Metabolic syndrome (increases progression risk despite initial zero score)

Patients Who Deferred Pharmacotherapy

• Canadian guidelines specifically recommend repeat scans after CAC = 0 when personal risk factors are present or pharmacotherapy was initially deferred 2
• This applies particularly when the initial zero score was used to justify withholding statin therapy 2

High-Risk Patients (≥20% 10-Year ASCVD Risk)

• Warrant repeat scanning at 3 years regardless of initial score 2

When NOT to Repeat CAC

Contraindications to Rescanning

• Patients already on optimal medical therapy with high CAC scores (>400) 1, 2
• Symptomatic patients who require functional testing or invasive evaluation rather than repeat calcium scoring 1
• Any interval <3 years from initial scan, as progression data is unreliable over shorter periods 1, 3

Canadian Guideline Exception

• Canadian guidelines do not recommend repeat scans after CAC = 0 unless personal risk factors are present or pharmacotherapy was deferred 1
• This represents a more conservative approach compared to ACC/AHA recommendations 1

Critical Caveats and Pitfalls

Do Not Down-Classify Risk Despite CAC = 0 in:

• Persistent smokers (may harbor noncalcified plaque) 2
• Diabetic patients (increased thrombotic risk independent of calcium) 2
• Patients with chronic inflammatory conditions (increased risk despite zero calcium) 2
• Strong family history of premature ASCVD (genetic risk not reflected in calcium score) 2

Statin Therapy Effects on Serial Scanning

• Prolonged statin therapy may have procalcific effects on coronary atheromas and can increase CAC 2
• Interpretation of serial CAC scores should account for statin use, as progression may reflect plaque stabilization rather than worsening disease 2
• Research shows statin-treated patients demonstrate 15% annual increase versus 39% in untreated patients, representing a 61% reduction in progression rate 4

Cost and Insurance Considerations

• Repeat CAC testing is generally considered inappropriate by some guidelines and may not be covered by insurance 2
• Clinical utility must justify the expense, as costs are often borne entirely by the patient 5
• Discussion regarding implications of repeat CAC results should occur before testing is recommended 5

Algorithmic Approach to Repeat CAC Timing

Step 1: Assess Initial CAC Score

• CAC = 0 → Proceed to Step 2
• CAC 1-99 → 3-5 years if results would change management
• CAC 100-400 → 3-5 years (3 years if diabetic or LDL-C ≥70)
• CAC >400 → Generally do not repeat

Step 2: For CAC = 0, Assess Risk Factors

• Low risk (<5% 10-year ASCVD) without risk enhancers → 5-7 years 2
• Borderline/intermediate risk (5-19.9%) → 3-5 years 2
• High risk (≥20%) → 3 years 2
• Presence of diabetes, smoking, inflammatory conditions, or family history → 3-5 years 2

Step 3: Consider Whether Results Would Change Management

• If patient already on optimal therapy → Do not repeat 2
• If progression would support treatment intensification → Proceed with repeat at appropriate interval 2
• If patient deferred pharmacotherapy based on CAC = 0 → Repeat in 3-5 years 2