Understand your coronary artery calcium score with MESA-based percentiles by age, sex, and ethnicity.
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Agatston Score
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10-Year ASCVD Risk
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A coronary artery calcium (CAC) score, also called an Agatston score, measures the amount of calcified plaque in your coronary arteries using a non-contrast, ECG-gated CT scan. The scan takes about 10 minutes with no injections, dye, or contrast agent. The resulting score reflects the total area and density of calcium deposits across all four major coronary arteries (left main, left anterior descending, circumflex, and right coronary artery).
The Agatston scoring method, developed in 1990 by cardiologist Arthur Agatston and radiologist Warren Janowitz, remains the reference standard for CAC quantification. The original method used electron beam CT with 3mm slice thickness, and has since been adapted for modern multidetector CT scanners at 2.5mm or 3mm slices with 120 KVp.
The calculation works as follows: the CT scan identifies calcified lesions in the coronary arteries using a detection threshold of 130 Hounsfield Units (HU). Only contiguous voxels totaling at least 1 mm² in area are counted as lesions, which helps filter out image noise. For each individual lesion, the score is calculated by multiplying the lesion area (in mm²) by a density weighting factor based on the peak HU within that lesion:
For example, a 15 mm² lesion with a peak density of 250 HU would receive a score of 15 x 2 = 30. A 10 mm² lesion with peak density of 450 HU would score 10 x 4 = 40. The total Agatston score is the simple sum of all such lesion scores throughout the heart.
An important nuance in current research: the Agatston score weights higher density calcium more heavily, but emerging MESA data shows that higher calcium density is actually associated with more stable plaque and fewer cardiovascular events. Denser calcified plaques have smaller lipid cores and are less likely to rupture than less dense plaques. This means the Agatston score may paradoxically upweight the "safer" component of calcification. Despite this limitation, the Agatston score remains the clinical standard because of its vast evidence base and strong overall predictive power.
The Multi-Ethnic Study of Atherosclerosis (MESA), which studied over 6,800 participants across four ethnic groups, found significant differences in calcium distribution. White men consistently had the highest calcium scores at every age, with Hispanic men second highest. Black men had the lowest scores at younger ages, and Chinese Americans had the lowest at older ages. For women, White women had the highest levels while Hispanic women generally had the lowest.
Crucially, despite these differences in calcium burden, MESA found that CAC predicts cardiovascular events with the same magnitude of effect across all races, age groups, and both sexes. The absolute score thresholds (0, 100, 400) work consistently regardless of demographics, making CAC one of the most universally useful risk prediction tools available.
CAC = 0: In MESA, 10-year ASCVD event rates were almost exclusively below 5%. Approximately 50% of MESA participants had zero calcium. A zero score is the strongest negative risk predictor and can be used to defer statin therapy for at least 5 years (the "warranty period" of a zero score).
CAC 1-99: Any detectable calcium is prognostically significant. The 2018 ACC/AHA guidelines state that CAC 1-99 favors statin therapy in patients at borderline (5-7.5%) or intermediate (7.5-20%) 10-year risk.
CAC ≥ 100 or ≥ 75th percentile: In MESA, all participants with CAC ≥ 100 had 10-year ASCVD event rates consistently above 7.5%, regardless of demographic subgroup. This is the key threshold identified by ACC/AHA guidelines as warranting statin therapy.
CAC ≥ 300-400: 10-year event rates in MESA ranged from 13.1% to 25.6%. Participants with CAC > 400 had hazard ratios exceeding 20x compared to those with CAC = 0.