1. What is the Friedewald Equation?

The Friedewald equation is a formula used to estimate LDL cholesterol (LDL-C) levels from measurements of total cholesterol (TC), HDL cholesterol (HDL-C), and triglycerides (TG). It provides a practical alternative to direct LDL measurement when resources are limited.

2. How Does the Calculator Work?

The calculator uses the Friedewald equation:

Where:

• \( TC \) — Total cholesterol (mg/dL)
• \( HDL-C \) — HDL cholesterol (mg/dL)
• \( TG \) — Triglycerides (mg/dL)

Explanation: The equation estimates LDL cholesterol by subtracting HDL cholesterol and VLDL cholesterol (estimated as TG/5) from total cholesterol.

3. Importance of LDL-C Calculation

Details: LDL cholesterol is a major risk factor for cardiovascular disease. Accurate estimation helps in assessing cardiovascular risk and guiding treatment decisions for cholesterol management.

4. Using the Calculator

Tips: Enter total cholesterol, HDL cholesterol, and triglycerides in mg/dL. All values must be valid (positive numbers). Note: This equation is not valid when triglycerides exceed 400 mg/dL.

5. Frequently Asked Questions (FAQ)

Q1: When should the Friedewald equation not be used?
A: The equation should not be used when triglyceride levels exceed 400 mg/dL, in non-fasting samples, or in patients with certain conditions like dysbetalipoproteinemia.

Q2: What are normal LDL cholesterol values?
A: Optimal LDL cholesterol is less than 100 mg/dL. Values between 100-129 mg/dL are near optimal, 130-159 mg/dL are borderline high, 160-189 mg/dL are high, and 190 mg/dL and above are very high.

Q3: How accurate is the Friedewald equation?
A: The equation provides a reasonable estimate in most cases but may underestimate LDL-C at lower levels. Direct measurement is preferred when precise values are needed.

Q4: Are there alternative equations for LDL estimation?
A: Yes, newer equations like the Martin/Hopkins method and the Sampson equation have been developed to improve accuracy, especially at low LDL and high triglyceride levels.

Q5: Should fasting be required for this calculation?
A: Yes, triglyceride levels are affected by recent food intake, so fasting for 9-12 hours is recommended for accurate LDL estimation using this equation.