Coronary Artery Calcium Scoring: What Your Score Means and When It Is Used
The coronary artery calcium (CAC) score measures calcified plaque in the heart's arteries with a non-contrast CT scan. Adding it to standard risk factors improves the prediction of heart events,1,3 and the 2026 US dyslipidemia guideline, which replaced the 2018 cholesterol guideline,6,4 uses it selectively when a treatment decision is uncertain.7
- A score of zero is reassuring: among 44,052 people referred for scans, those with no calcium had an all-cause death rate of 0.87 per 1,000 person-years, versus 7.48 for scores above 10, although smoking and diabetes still predicted deaths among people with zero scores.5
- In the Multi-Ethnic Study of Atherosclerosis (MESA), coronary events were 7.7 times as likely with scores of 101 to 300, and 9.7 times as likely above 300, as with no calcium, across white, Black, Hispanic and Chinese participants.3
- Under the 2026 US dyslipidemia guideline, a calcium score is used selectively when a treatment decision is uncertain: a score of zero may support deferring treatment in selected people without major high-risk conditions, and detectable calcium increasingly favours treatment as the score rises.7
- The score adds up the calcified lesions found on the scan, weighted by their size and density.2
- In MESA, adding the calcium score to standard risk factors moved more people into clearly high- or low-risk groups: 23% more of those who later had heart events were reclassified as high risk, and 13% more of those without events as low risk.1
Standard heart-risk calculators estimate risk from risk factors such as blood pressure, cholesterol, smoking, age, sex and diabetes. The calcium score adds a direct measure of calcified plaque. In MESA, adding it to a model built on traditional risk factors significantly improved risk classification and placed more people in the highest and lowest risk categories.1
What the CAC Score Measures
The Agatston method, developed with ultrafast CT in 1990, calculates the score from the number, area and peak density of the calcified lesions in the coronary arteries. In the original study, scores differed significantly between people with and without coronary heart disease in every decade of age studied.2 A score of zero means that no calcified plaque was detected.
The scan is a non-contrast CT of the chest timed to the heartbeat, so no dye is injected. Ask the imaging centre about the radiation dose and the cost, which vary between centres.
The MESA Data: Why CAC Is Unique
The Multi-Ethnic Study of Atherosclerosis (MESA) scanned 6,722 adults without heart disease, of whom 38.6% were white, 27.6% Black, 21.9% Hispanic and 11.9% Chinese, and followed them for a median of 3.8 years. Compared with people with no coronary calcium, the adjusted risk of a coronary event was 7.73 times higher with scores of 101 to 300 and 9.67 times higher with scores above 300. Each doubling of the score raised the risk of a major coronary event by 15% to 35% across the four groups, and adding the score to standard risk factors improved prediction.3
A score of zero deserves emphasis. Among 44,052 people without symptoms who were referred for testing, 45% had no detectable calcium. Their all-cause death rate was 0.87 per 1,000 person-years, compared with 1.92 for scores of 1 to 10 and 7.48 for scores above 10. Smoking and diabetes were still linked to deaths among people with zero scores, so a zero score is less reassuring for smokers and people with diabetes.5
Who Should Get a CAC Score
The 2026 US dyslipidemia guideline replaced the 2018 cholesterol guideline.6 It estimates 10-year risk with the PREVENT-ASCVD equations, which replaced the older pooled cohort equations, and groups it as low (under 3%), borderline (3% to under 5%), intermediate (5% to under 10%) or high (10% or more). A calcium score is meant to be used selectively, when the decision to start or intensify cholesterol-lowering treatment is still uncertain, not as a screening test for everyone. A score of zero may support temporarily deferring treatment in selected people without major high-risk conditions, while detectable calcium increasingly favours treatment as the burden rises, and a score of 1,000 or more marks extreme risk, with an LDL cholesterol goal below 55 mg/dL.7 The guideline also restores LDL goals in prevention: generally below 100 mg/dL at borderline or intermediate risk and below 70 mg/dL at high risk.7 Under the 2018 guideline, the score was suggested for adults 40 to 75 with a 10-year risk of 7.5% to 19.9% on the older equations.4
At borderline or intermediate risk, the estimate is weighed with risk-enhancing factors, including a premature family history of heart disease, persistently high LDL cholesterol, chronic inflammatory disease, chronic kidney disease, adverse pregnancy-related conditions and selected lipid tests. Lipoprotein(a) of 125 nmol/L (50 mg/dL) or more is one of them, and the guideline recommends measuring lipoprotein(a) at least once in adulthood.7
CAC Score Interpretation
| CAC score | What it means | 2026 guideline (used when a treatment decision is uncertain) |
|---|---|---|
| 0 | No calcified plaque detected | May support temporarily deferring treatment in selected people without major high-risk conditions |
| 1-99 | Some calcified plaque | Detectable calcium favours treatment |
| 100 or more, or at or above the 75th percentile | More calcified plaque | Favours treatment more strongly as the score rises; 1,000 or more is extreme risk, with an LDL goal below 55 mg/dL |
Actions summarize the 2026 US dyslipidemia guideline as described in a 2026 review.7
Put this research into practice: What Should I Test Next? · Biomarker Reference Tool
References
- 1Polonsky TS, et al. "Coronary artery calcium score and risk classification for coronary heart disease prediction." JAMA. 2010;303(16):1610-6. PubMed · DOI
- 2Agatston AS, et al. "Quantification of coronary artery calcium using ultrafast computed tomography." J Am Coll Cardiol. 1990;15(4):827-32. PubMed · DOI
- 3Detrano R, et al. "Coronary calcium as a predictor of coronary events in four racial or ethnic groups." N Engl J Med. 2008;358(13):1336-45. PubMed · DOI
- 4Grundy SM, et al. "2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines." Circulation. 2019;139(25):e1082-e1143. PubMed · DOI
- 5Blaha M, et al. "Absence of coronary artery calcification and all-cause mortality." JACC Cardiovasc Imaging. 2009;2(6):692-700. PubMed · DOI
- 6Blumenthal RS, et al. "2026 ACC/AHA/AACVPR/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Dyslipidemia: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines." Circulation. 2026;153(17):e1154-e1276. PubMed · DOI
- 7Sabouret P, et al. "The 2026 ACC/AHA Dyslipidemia Guideline: A Critical and Transatlantic Perspective on Personalized Lipid Management." Life (Basel). 2026;16(9). PubMed · DOI
