When should I get a coronary calcium score?

When to Get a Coronary Artery Calcium Score

Coronary artery calcium (CAC) scoring should be obtained in asymptomatic adults aged 40-75 years with intermediate cardiovascular risk (7.5%-20% 10-year ASCVD risk) when the decision about statin therapy remains uncertain after initial risk assessment. 1

Primary Indications for CAC Scoring

Intermediate-Risk Patients (The Sweet Spot)

• CAC scoring is most valuable for asymptomatic adults with 10-20% 10-year ASCVD risk where treatment decisions are genuinely uncertain 1
• This represents the population where CAC can reclassify more than half of patients and fundamentally alter management decisions 2
• Age ≥40 years is the minimum threshold across all major guidelines 1

Borderline-Risk Patients (Selected Cases)

• Consider CAC in adults with 5-7.5% 10-year ASCVD risk who have risk-enhancing factors 1
• Risk-enhancing factors include:
  • Family history of premature ASCVD 1
  • Persistently elevated LDL-C ≥160 mg/dL or triglycerides ≥175 mg/dL 1
  • Chronic kidney disease 1
  • Metabolic syndrome 1
  • South Asian ethnicity 1
  • Elevated lipoprotein(a) >50 mg/dL or hs-CRP ≥2.0 mg/L 1
  • Conditions specific to women (preeclampsia, premature menopause) 1
  • Inflammatory diseases (rheumatoid arthritis, psoriasis, HIV) 1

Low-Risk Patients (Very Limited Use)

• Generally NOT indicated for patients with <5% 10-year ASCVD risk 3, 2
• Exception: May be reasonable in low-risk patients with strong family history of premature CAD, but only if this would genuinely change management decisions 1
• A 41-year-old woman with 0.4% 10-year risk and family history alone does NOT meet criteria for CAC scoring 3

Special Populations

Diabetes Mellitus:

• Consider CAC in younger diabetic patients (Type 1 DM <35 years, Type 2 DM <50 years) with diabetes duration <10 years and no other risk factors 1
• Reasonable for diabetic patients aged 40-60 years when treatment decisions are uncertain 1

High-Risk Patients Reluctant to Accept Treatment:

• CAC may be indicated when high-risk patients refuse recommended statin therapy, as a CAC >100 may motivate adherence 1

When NOT to Get CAC Scoring

Absolute Contraindications

• Patients with known clinical ASCVD (prior MI, stroke, revascularization) - they already need maximal therapy 1
• Very low-risk patients (<5% 10-year risk) without risk-enhancing factors - radiation exposure cannot be justified 3
• Very high-risk patients (>20% 10-year risk) - they already need aggressive treatment regardless of CAC 4
• Patients already on optimal medical therapy where results would not change management 2

Relative Contraindications

• Age <40 years for most patients (very low prevalence of detectable calcium) 3
• Patients unwilling to consider statin therapy regardless of results 4
• When the result would not influence clinical decision-making 4

How CAC Results Guide Management

CAC = 0 (Very Low Risk)

• Downgrade risk and withhold statin therapy in most cases 1
• 10-year event rate only 1.5-3.0% 1
• Important exceptions where statins may still be considered despite CAC = 0: 1
  • Active smoking
  • Diabetes mellitus
  • Family history of premature CHD
• Repeat CAC in 3-7 years if risk factors persist 1

CAC = 1-99 (Mild Elevation)

• Favors statin therapy, especially for patients aged >55 years 1
• Modest risk reclassification upward 1
• In intermediate-risk patients with CAC 1-99, observed event rate is 6.5-10.4% 1
• Consider repeating CAC in 3-5 years if treatment deferred 1

CAC ≥100 or ≥75th Percentile (High Risk)

• Initiate moderate-to-high intensity statin therapy 1
• Event rate ≥20 per 1000 person-years, approximating secondary prevention population 1
• Number needed to treat with statin = 30 to prevent one ASCVD event over 5 years 2

CAC ≥300-400 (Very High Risk)

• High-intensity statin therapy strongly recommended 1
• Consider aspirin 81 mg daily per some specialty guidelines 1

CAC ≥1000 (Extremely High Risk)

• Should be considered a distinct patient group requiring aggressive risk factor modification 5
• High-intensity statin therapy mandatory 1

Common Pitfalls to Avoid

Pitfall #1: Ordering CAC in truly low-risk patients

• A patient with <5% 10-year risk and no risk-enhancing factors should NOT get CAC 3
• The radiation exposure (approximately 1.5 mSv) cannot be justified 3

Pitfall #2: Ignoring CAC >0 in "low-risk" patients

• Any detectable calcium (CAC >0) indicates definite atherosclerosis and should not be dismissed, even if traditional risk calculators suggest low risk 2
• CAC represents only ~20% of total atherosclerosis burden 2

Pitfall #3: Ordering CAC when results won't change management

• Always counsel patients BEFORE testing that results may lead to statin therapy 4
• If patient refuses statins regardless of results, don't order the test 4

Pitfall #4: Repeating CAC too soon

• Minimum interval between scans should be 3-5 years 1, 2
• Serial CAC has limited utility in patients already on optimal medical therapy 2

Pitfall #5: Confusing CAC with degree of stenosis

• CAC indicates atherosclerosis burden but does NOT correlate with degree of luminal narrowing 2
• Asymptomatic patients with elevated CAC do not routinely need stress testing or angiography 1