Lipoprotein quantification: an electrophoretic method compared with the Lipid Research Clinics method.

Abstract

We compared a turbidimetric electrophoretic method (Lipidophor) for lipoprotein quantification with the standardized Lipid Research Clinics (LRC) method. In the Lipidophor procedure, major lipoproteins are separated by electrophoresis on agarose gels, precipitated on the gels with phosphotungstate-Mg2+ reagent, and the resulting turbidity is measured densitometrically. Measurements of relative turbidity were converted into lipoprotein cholesterol values by the use of numeric constants provided by the manufacturer. Among-day CVs (n = 46) for the Lipidophor method were 6.0%, 3.6%, and 9.9% for cholesterol in the alpha-, beta-, and pre-beta lipoproteins, respectively. The Lipidophor alpha-cholesterol was significantly lower (n = 171 specimens) than the LRC high-density lipoprotein (HDL) cholesterol (514 vs 586 mg/L), and beta-cholesterol was significantly higher than the corresponding LRC low-density lipoprotein (LDL) cholesterol values (1505 vs 1409 mg/L). The linear relation between the two methods for lipoprotein cholesterol quantification is as follows: Lipidophor alpha = 0.77 LRC HDL + 63 mg/L with correlation coefficient (r) of 0.87; Lipidophor beta = 0.95 LRC LDL + 166 mg/L (r = 0.96); Lipidophor pre-beta = 0.57 LRC very-low-density lipoprotein + 39 mg/L (r = 0.82). We derived a revised algorithm for estimating lipoprotein cholesterol from turbidity measurements. Lipoprotein cholesterol values by the Lipidophor method agree well with those obtained by the LRC method when these constants are used.