Quantitative determination of cholesterol in lipoprotein fractions by electrophoresis

The Helena REP cholesterol profile system (Helena Laboratories, Beaumont, TX) separates VLDL, LDL, HDL and Lp(a) by agarose gel electrophoresis, and quantitates cholesterol by enzymatic staining and densitometry. We compared results by electrophoresis to combined ultracentrifugation/precipitation (beta-quantification, BQ) for VLDL, LDL, and HDL cholesterol and to immunonephelometry for Lp(a) mass (Behring Diagnostics, Westwood, MA) in serum from 64 patients with a variety of lipid disorders. There was good agreement between methods, with a mean bias of -0.19 (-7.3), 0.09 (3.5), and 0.09 (3.4) mmol/l (mg/dl) for VLDL, HDL, and LDL cholesterol for electrophoresis vs. BQ. These differences were significant for HDL and VLDL cholesterol (P < 0.001), but not for LDL cholesterol measurement (P > 0.05). There was also good correlation between methods with coefficients of 0.83, 0.92, 0.91, and 0.97 for VLDL, HDL, Lp(a), and LDL, respectively. Our data indicate that this method can accurately and precisely measure LDL cholesterol directly in fresh serum from patients with a wide range of triglyceride values. However, HDL cholesterol measurement did not meet NCEP guidelines for precision and accuracy. Also, the poor resolution of VLDL and LDL in some specimens is a concern.