How is the Framingham score used to determine statin (HMG-CoA reductase inhibitor) indication?

Using the Framingham Score to Determine Statin Indication

The Framingham Risk Score (FRS) is used to identify patients with a 10-year cardiovascular risk ≥7.5% who should receive statin therapy for primary prevention, even when LDL-C levels are between 70-189 mg/dL. 1

Risk Assessment Using Framingham Risk Score

The Framingham Risk Score calculates a patient's 10-year risk of developing cardiovascular disease based on several risk factors:

• Age
• Sex
• Total cholesterol
• HDL cholesterol
• Systolic blood pressure (treated or untreated)
• Smoking status
• Diabetes status

Risk Categories and Statin Recommendations

1. High Risk (≥20% 10-year risk or CVD equivalent)

   • LDL-C goal: <100 mg/dL (or optionally <70 mg/dL for very high risk)
   • Recommendation: Moderate to high-intensity statin therapy 1
   • Examples of CVD equivalents: diabetes, established cardiovascular disease

2. Moderately High Risk (10-19.9% 10-year risk with ≥2 risk factors)

   • LDL-C goal: <130 mg/dL (or optionally <100 mg/dL)
   • Recommendation: Moderate-intensity statin therapy 1

3. Moderate Risk (≤2 risk factors with <10% 10-year risk)

   • LDL-C goal: <130 mg/dL
   • Recommendation: Consider statin therapy if LDL-C ≥160 mg/dL after lifestyle modifications 1

4. Low Risk (0-1 risk factor)

   • LDL-C goal: <160 mg/dL
   • Recommendation: Consider statin therapy if LDL-C ≥190 mg/dL 1

Current Guideline Recommendations

According to the 2016 US Preventive Services Task Force (USPSTF) recommendation statement, statin therapy is indicated for:

1. Adults aged 40-75 years without history of CVD who have:

   • One or more CVD risk factors (dyslipidemia, diabetes, hypertension, or smoking), AND
   • A calculated 10-year CVD event risk of ≥7.5% using the Pooled Cohort Equations risk calculator 1

2. Adults with LDL-C >190 mg/dL (regardless of risk score)

3. Adults with diabetes (depending on 10-year CVD risk)

Different Approaches by Various Guidelines

Different organizations have varying thresholds for statin initiation based on Framingham risk:

• ACC/AHA: Recommends statin therapy for primary prevention when 10-year risk ≥7.5% (using Pooled Cohort Equations) 1

• Canadian Cardiovascular Society: Uses Framingham risk with thresholds of:

  • ≥20% 10-year risk: Statin therapy recommended
  • 10-20% risk with LDL-C 135-190 mg/dL: Statin therapy recommended
  • <10% risk: Statin therapy only for genetic hypercholesterolemia or LDL-C ≥193 mg/dL 1

• UK National Institute for Health and Care Excellence: Recommends statin therapy for adults ≥40 years with ≥10% 10-year CVD risk (using QRISK2 assessment tool) 1

Practical Application of Framingham Risk Score

1. Calculate the Framingham Risk Score using the appropriate tables for men and women 1

   • For men: Age (−9 to 13 points), total cholesterol (0 to 11 points), HDL-C (−1 to 2 points), smoking status (0 to 8 points), and systolic blood pressure (0 to 3 points)
   • For women: Similar categories with different point values

2. Determine 10-year risk based on total point score

   • Example: A total score of 12 points for men corresponds to a 10% 10-year risk

3. Apply risk threshold to determine statin indication

   • If risk ≥7.5-10% (depending on guideline used): Consider statin therapy
   • If risk ≥20%: Definitely recommend statin therapy

Beyond Framingham: Refining Risk Assessment

When Framingham risk is intermediate (5-20%), consider additional risk assessment tools:

• High-sensitivity C-reactive protein (hsCRP): Values >2 mg/L may elevate risk category 1

• Coronary artery calcium (CAC) scoring:

  • CAC = 0: May withhold statin therapy (even with intermediate FRS)
  • CAC 1-99: Consider statin therapy, especially in patients ≥55 years
  • CAC ≥100 or ≥75th percentile: Statin therapy recommended regardless of FRS 1

• Ankle-brachial index (ABI): Abnormal values may indicate higher risk 1

Common Pitfalls and Caveats

1. Undertreatment of high-risk patients with normal LDL-C: Studies show providers often fail to prescribe statins to patients with low LDL-C but high calculated CV risk 2

2. Overreliance on LDL-C levels alone: The Framingham risk incorporates multiple risk factors beyond just LDL-C

3. Not calculating risk routinely: Less than 20% of providers routinely calculate 10-year CV risk for their patients 2

4. Misclassification of risk: Some patients with low Framingham risk may have significant subclinical atherosclerosis (e.g., high coronary calcium scores) 3

5. Not considering additional risk factors: Family history of premature CVD, metabolic syndrome, and inflammatory markers should be considered when risk is borderline

Remember that providing the calculated CV risk score to clinicians has been shown to significantly improve appropriate statin prescribing, increasing statin use in high-risk patients and decreasing it in low-risk patients 2.