What is the method to calculate Atherosclerotic Cardiovascular Disease (ASCVD) risk?

How to Calculate ASCVD Risk

Use the ACC/AHA Pooled Cohort Equations to calculate 10-year ASCVD risk by entering seven clinical variables into the calculator, which applies race- and sex-specific coefficients through a validated mathematical formula to estimate the probability of a first hard atherosclerotic cardiovascular disease event within 10 years. 1

Required Input Variables

You need to collect the following seven parameters to calculate ASCVD risk 2:

• Age: 40-79 years (the calculator is only validated for this age range) 2
• Sex: Male or female 2
• Race: Non-Hispanic White or Non-Hispanic African American (other racial/ethnic groups lack sufficient validation data) 1, 2
• Total cholesterol: In mg/dL 1, 2
• HDL cholesterol: In mg/dL 1, 2
• Systolic blood pressure: In mmHg 1, 2
• Antihypertensive treatment status: Yes or no 1, 2
• Diabetes mellitus: Yes or no 1, 2
• Current smoking status: Yes or no 1, 2

The Mathematical Calculation Process

The Pooled Cohort Equations use a stepwise calculation approach 1:

1. Transform variables to natural logarithms: Calculate Ln(age), Ln(total cholesterol), Ln(HDL-C), and Ln(systolic BP) 1

2. Calculate interaction terms: Multiply natural log values for age-related interactions (e.g., Ln[Age] × Ln[Total Cholesterol]) 1

3. Apply race- and sex-specific coefficients: Multiply each transformed variable and interaction term by the appropriate coefficient from the race-sex specific equation 1

4. Sum the products: Add all the coefficient × value products to get the "Individual Sum" 1

5. Apply the final formula: The 10-year ASCVD risk = 1 − S₁₀^(e^(Individual Sum − Mean X'B)) 1

   • Where S₁₀ is the race- and sex-specific baseline 10-year survival rate
   • Mean X'B is the race- and sex-specific mean coefficient sum

Practical Implementation

In clinical practice, use an online calculator or electronic medical record integration rather than calculating manually 1, 2. The ACC/AHA provides free online calculators and downloadable applications that automatically perform these complex calculations 1.

Clinical Example

For a 55-year-old individual with total cholesterol 213 mg/dL, HDL-C 50 mg/dL, untreated systolic BP 120 mmHg, no diabetes, and no smoking 1:

• White women: 2.1% 10-year ASCVD risk 1
• African-American women: 3.0% 10-year ASCVD risk 1
• White men: 5.3% 10-year ASCVD risk 1
• African-American men: 6.1% 10-year ASCVD risk 1

What the Risk Score Predicts

The Pooled Cohort Equations estimate the 10-year probability of hard ASCVD events, which include 1, 2:

• Nonfatal myocardial infarction 1, 2
• Death from coronary heart disease 1, 2
• Fatal or nonfatal stroke 1, 2

Risk Stratification Thresholds for Treatment Decisions

The ACC/AHA guidelines use calculated risk to guide statin therapy decisions 3, 2:

• ≥7.5% 10-year risk: Statin therapy recommended for primary prevention in adults aged 40-75 years 3, 2
• 5-7.5% risk: Borderline/intermediate risk; consider risk-enhancing factors and shared decision-making 2
• <5% risk: Low risk; statin therapy generally not indicated based on risk score alone 3

Important Limitations and Caveats

Age is the dominant driver of calculated risk, which can result in older adults reaching treatment thresholds even with minimal other risk factors 4, 5. Among adults aged 60-69 years without CVD, 41% of men and 27% of women have calculated 10-year risk ≥10% even without traditional risk factors 2.

The equations may overestimate risk in contemporary populations, particularly at lower risk levels 1, 6. External validation studies have shown the Pooled Cohort Equations can overestimate actual event rates by 75-150% in some cohorts, though this finding is controversial and depends on the validation population used 1, 6.

The calculator has significant racial limitations: It is only validated for Non-Hispanic White and Non-Hispanic African American individuals 1, 2. The equations may overestimate risk in Asian-Americans and underestimate risk in South Asian-Americans 1.

For adults >75 years old, the calculator can be used but evidence for treatment decisions is limited, and statin therapy should only be considered after clinician-patient discussion in those with low calculated risk 3.

Alternative Risk Calculators

The 2024 PREVENT equations represent an updated alternative that removes race as a variable, adds kidney function and statin use, and generally estimates lower risk than the Pooled Cohort Equations 3, 7. The PREVENT equations estimate mean 10-year ASCVD risk at 4.3% compared to 8.0% using the Pooled Cohort Equations in the same population 7.

Risk Refinement Beyond the Calculator

For patients with borderline or intermediate risk (5-10%), consider additional risk-enhancing factors 3, 2:

• Coronary artery calcium (CAC) scoring: CAC = 0 confirms very low risk and supports deferring statin therapy; CAC ≥100 indicates higher risk (>7.5%) and favors statin initiation regardless of calculated risk score 3
• Family history of premature ASCVD 3, 2
• Chronic inflammatory conditions 3, 2
• South Asian ancestry 3, 2

Reassessment Frequency

Recalculate ASCVD risk periodically by reassessing 2:

• Blood pressure annually 2
• Lipid levels every 5 years 2
• Smoking status annually 2