CT Calcium Score Guideline

Indications for CAC Scoring

The American College of Cardiology recommends coronary artery calcium scoring as a reasonable tool to guide shared decision-making about statin therapy and intensification of preventive measures for asymptomatic individuals with borderline to intermediate cardiovascular risk (5-20% 10-year ASCVD risk) 1, 2
The American College of Radiology suggests that primary indications for CAC scoring include adults aged 40-75 years with intermediate risk (7.5-20% 10-year ASCVD risk) when treatment decisions are uncertain, borderline risk patients (5-7.5% 10-year risk) with risk-enhancing factors, and patients with family history of premature CAD even at lower calculated risk 1, 3
CAC scoring is also recommended for younger adults (30-49 years) with risk factors, where CAC >0 increases CAD events 3-12 fold and CAC >100 confers 10-fold higher mortality 4, 5

For patients with a CAC score of 0, statin therapy can generally be deferred unless the patient has diabetes, active smoking, family history of premature CAD, or chronic inflammatory conditions, with an event rate of 0.8 per 1,000 person-years and a number needed to treat for 5 years of 549 4, 5, 6
For patients with a CAC score of 1-99, statin therapy is favored, especially for patients aged >55 years, with an observed event rate of 10.4% and 10-year ASCVD rates by age of 3.8% (45-54 years), 6.5% (55-64 years), 8.3% (65-74 years), and 14.3% (75-85 years) 4, 5
For patients with a CAC score ≥100 or ≥75th percentile, statin therapy is strongly recommended, with an event rate of ≥20 events per 1,000 person-years and a number needed to treat for 5 years of 42 4, 5, 6

CAC scoring substantially improves risk prediction beyond traditional risk factors, with a net reclassification index of 25% in the MESA study and 24% high-risk and 19% low-risk in the Heinz Nixdorf Recall study 2, 3
The C-statistic improved from 0.76 to 0.81 (P<0.001) when CAC was added to risk models 2

The American College of Cardiology recommends against using CAC scoring in symptomatic patients to exclude obstructive CAD, as 19% of symptomatic CAC=0 patients had ≥50% stenosis in CORE64, and 3.5% of CONFIRM patients with chest pain and CAC=0 had ≥50% stenosis 2
Radiation exposure is now minimal with modern techniques, but remains a consideration, and incidental findings may trigger additional workup and patient anxiety 4