Should a 45‑year‑old asymptomatic adult with intermediate 10‑year atherosclerotic cardiovascular disease risk and no known coronary artery disease undergo coronary artery calcium (CAC) scoring by non‑contrast computed tomography?

Should a 45-Year-Old Asymptomatic Adult with Intermediate ASCVD Risk Undergo CAC Scoring?

Yes, coronary artery calcium scoring is reasonable and appropriate for this 45-year-old asymptomatic patient with intermediate 10-year ASCVD risk (6-10%) when decisions about statin therapy or other preventive interventions remain uncertain after discussing benefits, risks, and patient preferences. 1, 2

Primary Guideline Recommendation

• The 2010 ACC/AHA guideline provides a Class IIa recommendation (reasonable to perform) for CAC measurement in persons at intermediate risk (6% to 10% 10-year risk) for cardiovascular risk assessment. 1
• The 2019 ACC/AHA updated guidelines reaffirm that CAC scoring is most appropriate for asymptomatic adults aged 40-75 years with intermediate (7.5-20%) or borderline (5-7.5%) 10-year ASCVD risk when preventive treatment decisions are genuinely uncertain. 2
• This patient at 45 years old falls within the recommended age range (minimum 40 years for men, 50 years for women) where CAC has sufficient prevalence to provide meaningful risk stratification. 1, 2

Clinical Decision Algorithm

Step 1: Confirm patient meets appropriate use criteria

• Age 40-75 years ✓ (patient is 45)
• Asymptomatic ✓ (no chest pain or known CAD)
• Intermediate 10-year ASCVD risk ✓ (6-10% range specified)
• Uncertainty about preventive therapy ✓ (implied by the clinical question) 2

Step 2: Understand what the CAC score will tell you

• CAC quantifies coronary atherosclerotic burden and serves as a marker of vascular age, with cardiovascular risk increasing proportionally to the calcium score. 2
• The test definitively establishes presence or absence of coronary atherosclerosis, as calcification occurs exclusively in atherosclerotic lesions. 2
• CAC provides incremental prognostic information beyond traditional Framingham risk factors, with significantly higher area under the curve for predicting coronary events. 1, 3

Step 3: Interpret results for clinical management

• CAC = 0: Annual risk of cardiac death or MI <1% over 10 years; the patient can be reclassified to lower risk, potentially deferring statin therapy. 1, 2, 4

  • In pooled data from 27,622 asymptomatic patients, 11,815 subjects with CAC=0 had only 0.4% event rate over 3-5 years (49 events total). 1
  • Repeat scanning not needed for 5 years. 2

• CAC = 1-99: Low risk (<10% 10-year risk); presence of atherosclerosis confirmed with incrementally increased risk above zero. 2, 3

  • Consider lifestyle modifications and potentially statin therapy, especially if score ≥75th percentile for age/sex/race. 2
  • Repeat in 3-5 years if results might change treatment decisions. 2

• CAC = 100-399: Intermediate to moderately-high risk (10-20%); compared to CAC=0, relative risk is 4.3 (95% CI 3.5-5.2). 1, 2

  • Statin therapy benefits clearly exceed potential harm; initiate moderate-to-high intensity statin targeting ≥30-50% LDL-C reduction. 2
  • Number needed to treat for 5 years is 30-42. 2

• CAC ≥400: High risk (>20%); relative risk 7.2-10.8 compared to CAC=0, with 3-5 year CHD death/MI rates of 4.6-7.1%. 1, 2

  • Requires aggressive preventive therapy including high-intensity statins. 2
  • Consider screening for clinically silent ischemia (Class IIb recommendation). 1, 2

Technical Specifications

• Order as "CT Coronary Artery Calcium Score" or "Cardiac CT for Calcium Scoring" using ECG-gated multidetector computed tomography without contrast. 2
• Radiation exposure is low: typical effective dose 0.9-1.5 mSv, equivalent to 1-2 mammograms per breast. 1, 2
• Prospectively ECG-triggered scanning mode should be used to minimize radiation. 1
• The Agatston score is the standard method, defining calcific lesions as CT density >130 Hounsfield units with area >1 mm². 2, 4

Important Caveats and Limitations

• CAC reflects atherosclerotic burden, NOT degree of stenosis: Only 20% of total atherosclerosis contains calcium, and arterial remodeling often preserves lumen patency despite calcification. 2
• Cannot detect non-calcified plaque: Younger patients and those with acute coronary syndromes may have significant disease without calcification. 2
• Not appropriate for symptomatic patients: In symptomatic individuals with CAC=0,3.5% still had ≥50% stenosis and 1.4% had ≥70% stenosis in the CONFIRM registry. 2, 4
• Insurance coverage variable: Not all payors cover CAC scoring even when appropriately indicated; Medicare does not routinely cover it for screening. 2
• Incidental findings: Lung nodules detected in 0.4-16.5% of scans may trigger additional follow-up and patient anxiety. 2

Why This Patient Should Undergo CAC Scoring

• Intermediate-risk patients represent the strongest evidence-based indication for CAC scoring, with the greatest potential to reclassify risk and alter management. 1, 2
• The test provides information that cannot be obtained from traditional risk calculators alone, with studies demonstrating that CAC significantly improves prediction of coronary events beyond Framingham or PROCAM risk stratification. 1
• Cost-effectiveness is established for intermediate-risk patients when used to guide therapy, with typical cost <$100 at many imaging centers. 2
• At age 45, there is sufficient prevalence of detectable calcium to make the test informative, unlike in younger patients where scanning is generally not recommended. 1, 2

Contraindications for This Patient

• None identified: The patient does not fall into Class III (no benefit) categories, which include only persons at low risk (<6% 10-year risk). 1
• The patient is not symptomatic with chest pain, where CAC scoring would be inappropriate and functional testing or coronary CTA would be preferred. 1, 2

ICD-10 Coding for Ordering

• Use Z13.6 (encounter for screening for cardiovascular disorders) for asymptomatic screening in intermediate-risk patients. 2
• Alternative codes if specific risk factors present: Z82.49 (family history of ischemic heart disease), E78.5 (hyperlipidemia), or I25.10 (atherosclerotic heart disease without angina). 2