When should calcium scores be used in assessing cardiovascular disease risk?

When to Use Coronary Artery Calcium Scoring

Coronary artery calcium (CAC) scoring should be used primarily in asymptomatic adults at intermediate (7.5% to <20% 10-year ASCVD risk) or borderline (5% to <7.5% 10-year ASCVD risk) cardiovascular risk when there is uncertainty about initiating preventive therapies, particularly statins. 1

Primary Indications for CAC Scoring

Intermediate-Risk Patients (7.5% to <20% 10-year ASCVD risk)

• CAC scoring is reasonable for cardiovascular risk assessment in this population to guide decisions about statin therapy and other preventive interventions. 1
• The test can reclassify risk upward (particularly if CAC ≥100 Agatston units or ≥75th percentile for age/sex/race) or downward (if CAC = 0) in a significant proportion of individuals. 1
• CAC scoring has superior discrimination and risk reclassification compared to other subclinical imaging markers or biomarkers. 1

Borderline-Risk Patients (5% to <7.5% 10-year ASCVD risk)

• CAC measurement can be useful for select adults in this category, particularly when risk-enhancing factors are present (family history of premature ASCVD, chronic inflammatory disease, chronic kidney disease, metabolic syndrome, South Asian ancestry, history of preeclampsia, early menopause, or persistently elevated inflammatory markers). 1
• After considering clinically available risk-enhancing factors, if uncertainty persists, CAC testing is reasonable to more accurately reclassify the risk estimate. 1

Low-to-Intermediate Risk (6% to 10% 10-year risk)

• CAC measurement may be reasonable for cardiovascular risk assessment in this population. 1
• Selected low-risk adults (<5% 10-year risk) with strong family history of premature coronary heart disease may be considered for CAC scoring. 1

When NOT to Use CAC Scoring

Low-Risk Patients (<6% 10-year risk)

• Persons at low risk should NOT undergo CAC measurement for cardiovascular risk assessment. 1
• Exception: Those with strong family history of premature CHD may still be considered. 1

High-Risk Patients (≥20% 10-year risk)

• While not explicitly contraindicated, CAC scoring has limited utility in this population as they already warrant aggressive preventive therapy. 2
• CAC may still be justified if the patient is uncertain or reluctant about starting statins despite high calculated risk. 2

Age Restrictions

• CT scanning should generally not be performed in men <40 years old and women <50 years old due to very low prevalence of detectable calcium in these age groups. 1
• However, emerging data suggest CAC may refine risk estimates in younger adults (<45 years) and older adults (≥75 years), though more data are needed. 1

Symptomatic Patients

• CAC scoring should not be used in symptomatic patients with chest pain or known coronary artery disease, as CAC = 0 does not exclude obstructive disease. 3

Clinical Decision-Making Algorithm Based on CAC Results

CAC = 0

• Identifies individuals at lower risk of ASCVD events and death over a >10-year period. 1
• These patients appear to derive little or no benefit from statins for ASCVD risk reduction. 1
• Consider withholding statin therapy if no diabetes, family history of premature CHD, or smoking; reassess in 5-10 years. 2, 4
• Note: Absence of CAC does not rule out non-calcified plaque, and clinical judgment should prevail. 1

CAC 1-99

• Low risk (<10% at 10 years). 4
• Initiate statin therapy if patient ≥55 years old. 2
• Aspirin and statins are generally not recommended in patients with CAC <100. 4

CAC 100-400

• Intermediate risk (10-20% at 10 years). 4
• If ≥75th percentile for age/sex/race: Definitely initiate statin therapy. 2
• Statins may be reasonable if above 75th percentile; evidence for pharmacotherapy is less robust in this range. 4

CAC >400 or ≥100 AU

• High risk (>20% at 10 years). 4
• Definitely initiate statin therapy. 2
• Patients with elevated CAC will have event rates that clearly exceed benefit thresholds (≥7.5% in 10 years). 1

Special Considerations

Radiation Exposure

• The radiation dose in prospectively triggered CAC acquisition is low, with typical effective dose of 0.9-1.5 mSv (equivalent to 1-2 mammograms per breast). 1
• All current recommendations suggest prospective triggering be used for CAC scoring to minimize radiation exposure. 1

Cost-Effectiveness

• CAC scoring is now available at many imaging centers for <$100, making it a potentially cost-effective tool for allocation of preventive therapies, particularly in intermediate-risk patients. 1

Shared Decision-Making

• CAC results can help guide shared decision-making about statins or potentially even aspirin. 1
• The test is particularly valuable for motivating statin-reluctant patients and aiding decision-making in patients at risk of drug-drug interactions. 1

Documentation Requirements

• Clear documentation in the medical record is critical, including the patient's calculated 10-year ASCVD risk, current statin therapy status, and the reason for CAC scoring. 2
• Use appropriate ICD-10 codes: Z13.6 for cardiovascular screening in asymptomatic patients, or Z82.49 if family history of ischemic heart disease is the primary indication. 2, 3

Common Pitfalls to Avoid

• Do not use CAC scoring as universal screening—it should be selective and targeted to appropriate risk groups. 5
• Do not order CAC in symptomatic patients—3.5% of symptomatic patients with CAC = 0 still had ≥50% arterial stenosis. 3
• Do not assume CAC score correlates with degree of stenosis—CAC has poor specificity for diagnosing obstructive coronary artery disease. 3
• Do not ignore clinical context when CAC = 0—non-calcified plaques may still be present, particularly in younger patients or those with diabetes. 1