What is the American Heart Association (AHA)/American College of Cardiology (ACC) level of recommendation for requesting Computed Tomography (CT) coronary calcium scoring?

AHA/ACC Recommendation for CT Coronary Calcium Scoring

The ACC/AHA gives CT coronary artery calcium (CAC) scoring a Class IIa recommendation (Level of Evidence: B-NR) for asymptomatic adults aged 40-75 years at intermediate risk (7.5% to <20% 10-year ASCVD risk) or selected borderline risk patients (5% to <7.5% 10-year ASCVD risk) when treatment decisions remain uncertain. 1

Risk-Stratified Recommendations

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

• Class IIa recommendation: CAC scoring is reasonable as a guide for shared decision-making when decisions about preventive interventions (particularly statin therapy) are uncertain 1
• This represents the strongest recommendation level, indicating the benefit substantially outweighs the risk 1

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

• Class IIa recommendation: CAC scoring is reasonable in selected borderline risk adults when treatment decisions are uncertain 1
• Selection criteria include presence of risk-enhancing factors such as family history of premature CHD, persistently elevated LDL-C ≥160 mg/dL, metabolic syndrome, chronic kidney disease, or inflammatory diseases 1

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

• Class IIb recommendation: CAC measurement may be reasonable for cardiovascular risk assessment 1
• This is a weaker recommendation (Class IIb) compared to the intermediate risk group, indicating usefulness is less well established 1

Low Risk (<6% 10-year risk)

• Class III: No Benefit: Persons at low risk should NOT undergo CAC measurement for cardiovascular risk assessment 1
• Exception: May be appropriate in low-risk patients with a family history of premature coronary heart disease 2

Interpretation and Clinical Action Based on CAC Score

The 2019 ACC/AHA guidelines provide specific guidance on how to use CAC results 1:

CAC Score = 0

• It is reasonable to withhold statin therapy and reassess in 5-10 years 1
• Caveat: Higher-risk conditions override this recommendation—still consider statins if diabetes, family history of premature CHD, or cigarette smoking are present 1
• A zero score confers very low risk (<1% annually) for cardiac death or myocardial infarction 3

CAC Score = 1-99

• It is reasonable to initiate statin therapy for patients ≥55 years of age 1
• For younger patients with scores in this range, shared decision-making should incorporate other risk factors 1

CAC Score ≥100 or ≥75th Percentile

• It is reasonable to initiate statin therapy 1
• Scores >400 warrant consideration for screening for clinically silent ischemia 3

Important Clinical Caveats

Age Considerations

• Generally not recommended for men <40 years or women <50 years due to low prevalence of detectable calcium and radiation exposure concerns 1
• For younger patients (<45 years), reserve CAC scoring for those with multiple major ASCVD risk factors or family history of premature ASCVD 1

Radiation Exposure

• The radiation dose is relatively low (0.9-1.5 mSv), comparable to 1-2 mammograms 1
• All current recommendations mandate prospective ECG-triggering to minimize radiation 1

Critical Limitation

• CAC = 0 does NOT exclude non-calcified plaque or obstructive coronary disease 1, 3
• In symptomatic patients, 7-38% with CAC = 0 have obstructive disease 1
• CAC scoring measures calcified plaque burden, not degree of stenosis 3

Comparison with Earlier Guidelines

The 2010 ACC/AHA guidelines provided similar but slightly different risk thresholds 1:

• Class IIa: Intermediate risk (10% to 20% 10-year risk)
• Class IIb: Low-to-intermediate risk (6% to 10% 10-year risk)
• Class III: Low risk (<6% 10-year risk)

The 2019 update refined these categories and strengthened the recommendation by extending Class IIa to include selected borderline risk patients and providing more specific guidance on CAC score interpretation 1.

Practical Implementation

Before ordering CAC scoring, ensure 1, 2:

• The patient falls into intermediate or borderline risk category
• Treatment decisions (particularly statin initiation) are genuinely uncertain
• You are prepared to act on the results—either initiate or withhold therapy based on the score
• The patient understands that CAC scoring is primarily useful for risk stratification, not diagnosis of obstructive disease

The test should only be ordered if the result will change management decisions 4, 5.