1. What is the Friedewald Equation?

The Friedewald equation is a formula used to estimate low-density lipoprotein cholesterol (LDL-C) levels from measurements of total cholesterol (TC), high-density lipoprotein 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 (mmol/L)
• \( HDL-C \) — HDL cholesterol (mmol/L)
• \( TG \) — Triglycerides (mmol/L)

Explanation: The equation estimates LDL cholesterol by subtracting HDL cholesterol and VLDL cholesterol (estimated as TG/2.2) 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 lipid-lowering therapy decisions.

4. Using the Calculator

Tips: Enter total cholesterol, HDL cholesterol, and triglycerides in mmol/L. All values must be valid (greater than 0). Note: This equation is not valid when triglyceride levels exceed 4.5 mmol/L.

5. Frequently Asked Questions (FAQ)

Q1: When is the Friedewald equation not accurate?
A: The equation becomes less accurate when triglyceride levels exceed 4.5 mmol/L, in non-fasting samples, or in patients with certain metabolic disorders.

Q2: What are the limitations of this calculation?
A: The equation assumes a fixed ratio of triglycerides to VLDL cholesterol (5:1 in mg/dL or 2.2:1 in mmol/L), which may not hold true in all individuals.

Q3: How does this compare to direct LDL measurement?
A: Direct measurement is more accurate, especially when triglycerides are elevated, but the Friedewald equation provides a reasonable estimate in most routine clinical situations.

Q4: What are optimal LDL-C levels?
A: Optimal levels are generally below 2.6 mmol/L for most adults, and below 1.8 mmol/L for high-risk patients.

Q5: Should fasting samples be used?
A: Yes, fasting samples (8-12 hours) are recommended for accurate triglyceride measurement, which affects the LDL calculation.