What are the limitations of coronary calcium scoring?

Limitations of Coronary Calcium Scoring

Coronary artery calcium (CAC) scoring has significant limitations including radiation exposure, inability to detect non-calcified plaque in symptomatic patients, lack of randomized controlled trials demonstrating improved outcomes, and potential for triggering unnecessary downstream testing. 1

Key Limitations of CAC Scoring

Technical and Methodological Limitations

• Radiation exposure: While newer dose-reduction strategies have reduced radiation exposure to levels comparable to mammography, radiation remains a concern, especially for younger patients 1
• Cost barriers: Despite decreasing costs over recent decades, not all insurance providers cover CAC scoring, limiting accessibility for many patients 1
• Detection limitations: CAC scoring cannot detect non-calcified atherosclerotic plaque, which means the absence of calcium does not exclude obstructive coronary artery disease in symptomatic patients 1
• Scoring methodology issues: Traditional scoring methods have inherent weaknesses and limitations, with most being somewhat arbitrary rather than developed from robust conceptual models 2

Clinical Evidence Limitations

• Lack of randomized controlled trials: Despite extensive observational data demonstrating prognostic value, CAC scoring has not been evaluated in prospective randomized controlled trials for improving cardiovascular outcomes 1
• Calibration issues: The Pooled Cohort Equation used alongside CAC scoring may be suboptimally calibrated in modern populations compared to the older cohorts from which it was derived 1
• Limited evidence in certain populations: More data is needed to support CAC use in lower-risk women, younger adults (<45 years), and older adults (≥75 years) 1

Practical Clinical Concerns

• Incidental findings: Non-vascular incidental findings such as lung nodules (found in 0.4-16.5% of scans) or lung cancer (0.0-1.2%) can create patient anxiety and trigger additional follow-up testing 1
• Risk of overtreatment: In populations with higher socioeconomic position and continual access to preventive services, risk calculators may overestimate risk, potentially leading to overtreatment 1
• Potential for cascade testing: Inappropriate use in low-risk populations or misinterpretation of results can lead to unnecessary cardiac testing 3

Appropriate Use Considerations

CAC scoring should be limited to specific clinical scenarios:

• Most appropriate for asymptomatic adults aged 40-75 years with intermediate cardiovascular risk (7.5-20% 10-year ASCVD risk) 4
• May be considered in selected borderline-risk (5-7.5%) patients 1
• Not recommended for low-risk patients (<6% 10-year risk) 4
• Not recommended as a routine screening tool in asymptomatic patients with good functional capacity 1

Interpreting Results with Caution

• A CAC score of zero identifies individuals at lower risk of ASCVD events but does not rule out non-calcified plaque 1
• Clinical judgment about risk should prevail even with a zero score 1
• For symptomatic patients, additional testing may be necessary regardless of CAC score 1

Avoiding Common Pitfalls

• Avoid using CAC as a standalone test: Always integrate with clinical risk factors and traditional risk assessment tools
• Avoid routine rescanning: In patients with a CAC of 0, repeat testing should not be done sooner than 5 years; for positive scores, routine rescanning is not currently recommended 5
• Avoid testing without a plan: CAC scoring should only be undertaken if an alteration in therapy would be considered based on the test result 5
• Avoid inappropriate downstream testing: Current guidelines do not support routine testing for silent ischemia in asymptomatic patients with elevated CAC scores 1

CAC scoring remains a valuable risk stratification tool when used appropriately, but clinicians must be aware of these significant limitations to avoid misuse and potential harm to patients.