What is the reference method for lipoprotein analysis?

• A. Ultracentrifugation
• B. Precipitation
• C. Gel electrophoresis
• D. NMR spectroscopy

Answer: (A)

Separating lipoproteins by density using ultracentrifugation is the reference method because it physically fractionates the different lipoprotein classes (such as chylomicrons, VLDL, LDL, and HDL) based on their density. This direct, density-guided separation allows precise measurement of cholesterol or triglycerides in each fraction and provides a gold-standard standard against which other, faster methods can be compared. Although it is labor-intensive and requires specialized ultracentrifugation equipment, its accuracy and ability to yield true lipoprotein fractions make it the benchmark in reference analyses.

Other approaches used in routine or research settings, like precipitation methods, gel-based separation, or NMR, are more practical for quicker results but do not offer the same absolute fractionation accuracy and standardization as density-based ultracentrifugation. Precipitation can have incomplete or variable separations, gel electrophoresis provides profile information without exact fractional quantification, and NMR estimates particle characteristics but isn’t the traditional reference standard for lipoprotein analysis.