Variation in Different Lipoprotein Fractions if Estimated by Different Methodologies

Area of Science:

• Clinical Chemistry
• Cardiovascular Disease Biomarkers

Background:

• Lipid and lipoprotein levels are crucial for assessing coronary artery disease (CAD) risk.
• Friedewald's formula, used since 1972, estimates low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL) but has limitations.
• The formula relies on indirect calculations and does not account for all lipoprotein types, potentially introducing errors.

Purpose of the Study:

• To compare LDL and VLDL values calculated by Friedewald's formula with those obtained by direct homogenous assays and electrophoretic separation.
• To evaluate the accuracy of Friedewald's formula in determining lipoprotein levels for CAD risk assessment.

Main Methods:

• Sixty adult patients with triglyceride levels < 400 mg/dL were analyzed.
• LDL and high-density lipoprotein (HDL) cholesterol were measured using enzymatic assays with selective solubilization and antibody binding.
• Lipoprotein electrophoresis on agarose gel was performed, and values were compared with Friedewald's formula calculations.

Main Results:

• Friedewald's formula-calculated LDL values significantly differed from direct assay and electrophoresis (p < 0.001).
• Direct assay and electrophoresis LDL values showed no significant difference (p = 0.53).
• Calculated VLDL values also significantly differed from electrophoretic measurements (p < 0.001), and HDL values differed between direct and electrophoretic assays (p < 0.001).

Conclusions:

• Friedewald's equation yields erroneous lipoprotein values, particularly when intermediate-density lipoproteins are altered, as seen in conditions like diabetes mellitus.
• Even with low triglyceride levels, calculated lipoprotein values deviate from direct and electrophoretic measurements.
• Direct and electrophoretic assays offer more accurate assessments of lipoprotein levels compared to Friedewald's formula.