The Agatston score is the standard way to quantify coronary calcium. A calcified lesion is defined as ≥ 3 contiguous pixels with a CT density > 130 HU. The score for each lesion is the plaque area × a density cofactor (1–4, depending on peak attenuation). Individual lesion scores are summed across all coronary arteries to obtain the total per-patient Agatston score.
1 Risk stratification categories
A score > 300 predicts major adverse cardiovascular events (MACE) at rates similar to patients who have already had a prior myocardial infarction — a secondary prevention equivalent.
2 Clinical use
CAC scores are most useful for asymptomatic patients categorized as “intermediate” or “borderline” by traditional risk calculators — they’re what decides whether to start lipid-lowering therapy. Total scores are frequently compared to population databases to provide a percentile (by age, sex, and ethnicity) or an estimated arterial age.
See also: the ASCVD + statin recommender automatically incorporates a CAC score when one is provided.