What is the sensitivity and specificity of Coronary Artery Calcium (CAC) scores for detecting coronary artery disease?

Sensitivity and Specificity of Coronary Artery Calcium (CAC) Scores for Detecting Coronary Artery Disease

CAC scoring demonstrates high sensitivity (85-98%) but moderate specificity (40-75%) for detecting obstructive coronary artery disease, with the presence of any calcium (CAC>0) having excellent negative predictive value (96-99%) for ruling out significant coronary stenosis. 1

Diagnostic Performance of CAC Scoring

Sensitivity and Specificity Values

• According to the 2012 ACCF/AHA guidelines, based on data from large multicenter registries including 3,615 symptomatic patients, CAC scoring has:

  • Sensitivity: 85% for predicting obstructive CAD on invasive angiography
  • Specificity: 75% for predicting obstructive CAD on invasive angiography 1

• A meta-analysis of 18 studies with 10,355 symptomatic patients found that the presence of any coronary calcium (non-zero CAC score) had:

  • Sensitivity: 98% for detecting significant CAD
  • Specificity: 40% for detecting significant CAD 1

Negative Predictive Value

• The negative predictive value of CAC=0 for obstructive CAD is extremely high at 96-99%, making it particularly useful for ruling out disease 1, 2
• A 2023 registry-based study of 10,857 patients found that CAC=0 correctly ruled out obstructive CAD in 98.2% of symptomatic patients 2

Age-Related Considerations

• The sensitivity of CAC=0 for ruling out obstructive CAD is lower in younger patients (<45 years), at only 82.3%, despite maintaining a high negative predictive value of 98.9% 2
• This occurs because younger patients may have non-calcified atherosclerotic plaque that hasn't yet calcified 1

Clinical Implications

False Negatives

• Despite high sensitivity, false negatives do occur:
  • In the CONFIRM registry, among 10,037 symptomatic patients with CAC=0:
    • 13% had non-obstructive CAD
    • 3.5% had ≥50% stenosis
    • 1.4% had ≥70% stenosis on coronary CT angiography 1, 3
  • Documentation of obstructive CAD without CAC occurs more frequently in younger patients whose atherosclerotic plaque has not yet calcified 1

Prognostic Value

• Patients with CAC=0 and obstructive CAD (≥50% stenosis) have a 5.7-fold higher risk of adverse cardiovascular events compared to those with CAC=0 and no obstructive CAD 3
• The absence of CAC is associated with an extremely low annual event rate of 0.027% in asymptomatic individuals 4

Vessel-Specific vs. Whole-Heart Scoring

• Vessel-specific and lesion-specific CAC scores demonstrate superior diagnostic performance compared to whole-heart Agatston scores for predicting obstructive CAD 5
• Maximum lesion-specific Agatston score has better diagnostic accuracy than whole-heart scoring (area under ROC curve 0.71 vs 0.58) 5

Clinical Applications

Risk Stratification

• CAC scoring is most valuable in intermediate-risk patients (7.5-20% 10-year ASCVD risk) 6
• CAC=0 may allow for de-escalation of preventive therapies in certain patients 6
• CAC scores ≥100 reclassify patients to higher risk categories, warranting more aggressive preventive interventions 6

Limitations and Caveats

• A "positive" CAC score, even in upper quartiles, cannot be used as strong evidence of myocardial ischemia 1
• CAC scoring should not be performed in patients with known extensive calcification or high risk of CAD, as significant calcification can preclude accurate assessment of lesion severity 1
• In patients with high clinical suspicion of CAD, a CAC=0 does not reliably exclude obstructive disease 1

CAC scoring provides valuable diagnostic and prognostic information, particularly for ruling out significant CAD in appropriate populations, but clinicians should be aware of its limitations, especially in younger patients and those with high clinical suspicion of CAD.