When should a coronary artery calcium (computed tomography) score be ordered in asymptomatic adults aged 40‑75 years for cardiovascular risk assessment, including those with intermediate or borderline atherosclerotic cardiovascular disease risk, diabetes, or a strong family history of premature coronary disease?

When to Order CT Calcium Score

Order a coronary artery calcium (CAC) score for asymptomatic adults aged 40–75 years with intermediate (7.5%–19.9%) or borderline (5%–7.4%) 10-year ASCVD risk when uncertainty remains about initiating statin therapy after discussing benefits, risks, and patient preferences. 1

Primary Indications by Risk Category

Intermediate-Risk Adults (7.5%–19.9% 10-year ASCVD risk)

• This represents the strongest evidence-based indication for CAC scoring. Adults aged 40–75 years with LDL-C 70–189 mg/dL and intermediate risk should undergo CAC testing when statin therapy decisions remain uncertain after initial risk assessment. 1, 2
• CAC scoring provides the most accurate risk stratification in this population, with the capacity to meaningfully reclassify risk and guide preventive therapy decisions. 1, 3
• The ACC/AHA assigns a Class IIa recommendation (moderate-level evidence) for CAC scoring in this group. 1, 2

Borderline-Risk Adults (5%–7.4% 10-year ASCVD risk)

• Order CAC scoring when one or more risk-enhancing factors are present, including: 1, 2
  • Family history of premature ASCVD (men <55 years, women <65 years)
  • Persistently elevated LDL-C ≥160 mg/dL (4.1 mmol/L)
  • Metabolic syndrome
  • Chronic kidney disease
  • Chronic inflammatory disorders (rheumatoid arthritis, psoriasis, HIV)
  • History of preeclampsia or premature menopause
  • Elevated lipoprotein(a) >50 mg/dL (>125 nmol/L)
  • High-risk ethnicity (South Asian ancestry)
  • Persistently elevated triglycerides >175 mg/dL (2.0 mmol/L)

Low-Risk Adults (<5% 10-year ASCVD risk)

• Do not order CAC scoring routinely in low-risk individuals, as the test provides minimal actionable information and exposes patients to unnecessary radiation. 1, 2, 3
• Consider CAC scoring only in highly selected low-risk adults with a strong family history of premature CAD. 1, 2

High-Risk Adults (≥20% 10-year ASCVD risk)

• Do not order CAC scoring—high-intensity statin therapy is already indicated regardless of CAC results. 1, 4

Special Populations

Diabetes Mellitus

• Consider CAC scoring in younger diabetic patients to refine risk assessment: 2, 3
  • Type 1 diabetes <35 years with disease duration <10 years and no other major risk factors
  • Type 2 diabetes <50 years with disease duration <10 years and no other major risk factors
• Adults 30–39 years with long-standing diabetes (Type 1 >20 years or Type 2 >10 years) plus additional risk factors or microangiopathy may benefit from CAC scoring. 3
• Important caveat: Do not down-classify risk in diabetic patients with CAC=0, as they may harbor non-calcified plaques. 3

Older Adults (76–80 years)

• CAC scoring may be reasonable only to identify CAC=0 in order to support deferring statin therapy in patients with LDL-C 70–189 mg/dL. 1, 2
• Beyond age 80, CAC scoring is not recommended; treatment decisions should be based on functional status, life expectancy, and patient preferences. 2

Active Smokers with Elevated Cholesterol

• Active cigarette smoking overrides a CAC=0 result—do not defer statin therapy in current smokers even when CAC=0. 1, 4
• Smoking is a contraindication to withholding statin therapy in intermediate-risk patients, limiting the utility of CAC scoring in this population. 4
• If CAC scoring is performed and returns zero, initiate moderate-intensity statin therapy immediately and prioritize smoking-cessation counseling. 4

Contraindications and Inappropriate Use

Do NOT Order CAC Scoring in:

• Symptomatic patients (chest pain, known CAD)—CAC=0 does not exclude obstructive disease; 3.5% of symptomatic patients with CAC=0 have ≥50% stenosis. 1, 2, 3
• Patients with established ASCVD—these individuals already warrant aggressive preventive therapy. 1, 3
• Truly low-risk asymptomatic patients (<5% 10-year risk) without risk-enhancing factors—the test yield is extremely low and does not change management. 2, 3

Clinical Decision Algorithm

Step 1: Calculate 10-Year ASCVD Risk

• Use the ACC/AHA Pooled Cohort Equations for adults aged 40–75 years with LDL-C 70–189 mg/dL. 1, 2

Step 2: Apply Risk-Based Treatment Thresholds

• High risk (≥20%): Start high-intensity statin immediately; do not order CAC. 1, 4
• Intermediate risk (7.5%–19.9%): Conduct a structured discussion of statin benefits (20–30% relative risk reduction), adverse effects, and patient preferences. If uncertainty persists, order CAC scoring. 1, 2
• Borderline risk (5%–7.4%): Assess for risk-enhancing factors. If present and uncertainty remains, order CAC scoring. 1, 2
• Low risk (<5%): Do not order CAC unless a strong family history of premature CAD exists. 1, 2

Step 3: Interpret CAC Results and Initiate Therapy

CAC Score	10-Year Event Risk	Statin Recommendation	Intensity	Citation
0	1.5%–3.0%	Defer statin in most cases; reassess in 5–10 years. Exception: Do not defer in active smokers, diabetics, or those with premature family history.	—	[1,2,4]
1–99	6.5%–7.4%	Initiate statin, especially if age ≥55 years or score ≥75th percentile for age/sex/race.	Moderate-intensity (≥30% LDL-C reduction)	[1,2,4]
100–399	≥7.5% (≥20/1,000 person-years)	Initiate statin; this score reclassifies patients to high risk regardless of demographics.	Moderate-to-high intensity (30%–50% LDL-C reduction)	[1,2,4]
≥400	Very high (7.2–10.8× higher than CAC=0)	Initiate high-intensity statin; consider low-dose aspirin after bleeding-risk assessment.	High-intensity (≥50% LDL-C reduction)	[1,2,4]
≥300 (especially ≥1,000)	Extremely high	High-intensity statin is strongly recommended.	High-intensity	[1,4]

Repeat Scanning Intervals

• CAC = 0: Repeat in 5–10 years if risk factors persist (e.g., diabetes, smoking, chronic inflammatory disease, strong family history). 1, 2
• CAC = 1–99: Repeat in 3–5 years if results might change treatment decisions. 1, 2
• CAC ≥ 400: Do not repeat CAC scanning—patients are already classified as high risk and should receive aggressive therapy. 2
• Patients on optimal therapy: Do not repeat CAC within 3–5 years; progression is expected and does not indicate treatment failure. 2, 3

Critical Pitfalls to Avoid

• Do not use CAC to assess coronary artery stenosis. CAC quantifies atherosclerotic burden, not luminal narrowing; only ~20% of total atherosclerotic plaque contains calcium. 2, 4
• Do not defer statin therapy in active smokers with CAC=0—smoking overrides the protective implication of a zero score. 1, 4
• Do not order CAC in symptomatic patients—functional testing (stress myocardial perfusion imaging, stress echocardiography) or coronary CTA is preferred. 1, 2
• Do not ignore CAC >0 in "low-risk" patients—any measurable calcium indicates atherosclerosis and incremental risk above zero. 2, 3
• Do not repeat CAC too soon (<3–5 years) in patients already on optimal medical therapy. 1, 2

Technical Considerations

• Order the test as "CT Coronary Artery Calcium Score" or "Cardiac CT for Calcium Scoring" using ECG-gated multidetector computed tomography without contrast. 2
• Radiation exposure is low (0.37–1.5 mSv), equivalent to 1–2 mammograms per breast. 1, 2
• The Agatston score is the standard method, defining calcific lesions as CT density >130 Hounsfield units with area >1 mm². 1, 2

Aspirin Considerations

• Consider low-dose aspirin (81 mg daily) for patients with CAC ≥100, with stronger consideration when CAC ≥300, after individualized bleeding-risk assessment. 2, 4

Limitations of CAC Scoring

• CAC cannot detect non-calcified atherosclerotic plaques, which may be present in earlier stages of atherosclerosis. 1, 2
• CAC has poor specificity for diagnosing obstructive coronary artery disease due to the modest relationship between calcification and luminal obstruction. 1, 2
• Long-term statin therapy may have pro-calcific effects, leading to an increase in CAC scores over time; this does not indicate treatment failure. 2
• Nonvascular incidental findings (lung nodules in 0.4–16.5% of scans) may create patient anxiety and trigger additional follow-up. 2

Conflicting Evidence: USPSTF Dissent

• The 2018 USPSTF statement concludes that evidence is insufficient for adding CAC to traditional cardiovascular risk assessment in asymptomatic adults, asserting that the clinical meaning of risk reclassification by CAC remains largely unknown. 1
• However, this conflicts entirely with ACC/AHA, ESC, NLA, and SCCT guidelines, all of which advise consideration of CAC testing in select populations based on robust prognostic data from multicenter studies with up to 15-year follow-up. 1, 5