Determination of apolipoprotein B by kinetic (rate) nephelometry

Determination of apoB by rate nephelometry is a simple, rapid and precise method, which is also suitable for a routine laboratory. It can be standardized with lipoprotein-B or LDL fractions, but only if these fractions are diluted with fresh whole serum. The standardization is also valid for VLDL if the samples are diluted with hydroxypolyethoxydodecane (trade name: Thesit) in a concentration of 0.33 g/liter. Using rate nephelometry, a strong correlation between the contents of cholesterol and apoB of VLDL as well as of LDL can be demonstrated. Similar high correlations are achieved if apoB is determined chemically in isolated lipoprotein fractions. The ratio of apoB to cholesterol is constant but not the same in both VLDL and LDL. There is also a strong correlation between the concentration of apoB in whole serum with the LDL cholesterol values in a normotriglyceridemic population. Therefore, the assay of apoB in whole serum by rate nephelometry is proposed as a screening method for dyslipoproteinemia (increased concentrations of atherogenic lipoproteins at normal or elevated levels of cholesterol in plasma).