Determination of LDL Cholesterol and LDL Apolipoprotein B Following Precipitation of VLDL in Blood Serum with Phosphotungstic Acid/MgCk By H. Schriewer,

Summary: A method is described for the selective precipitation of VLDL in blood serum using phosphotung-stic acid/MgCl2. The method allows for the calculation of LDL apolipoprotein B äs well äs for the calculation of LDL cholesterol (following the additional determination of HDL cholesterol). Dependent on the triglyce-ride and the cholesterol content of the serum, three different procedures were developed using phosphotung-stic acid and MgCla in different concentrations in the precipitation assay. Within the tested ränge of 3—10 mmol/1 total cholesterol and 1—4 mmol/1 triglyceride in blood serum the VLDL were nearly completely precipitated with negligible coprecipitation of LDL and HDL, but 40—50 % coprecipitation of Lp(a). Regression analysis of the cholesterol values obtained by precipitation with phosphotungstic acid/MgCh (= serum cholesterol — LDL cholesterol), and the cholesterol values obtained by ultracentrifugation (d> 1.006 kg/l) revealed a good measure of agreement (r = 0.97, y = 0.93-h 0.35, n = 76). An equally good measure of agreement was found for the corresponding apolipoprotein B values (r = 0.96, y = l.03 — 0.2, n = 61). In the determination of LDL cholesterol a Variation coefficient of 4.3 % (n = 20) was found in relation to the precision in the series, and a Variation coefficient of 4.8 % (n = 25) in relation to day to day precision. Bestimmung von LDL-Cholesterin und LDL-Apolipoprotein B nach Fällung von VLDL im Blutserum mittels Phosphorwolf ramsäure/MgCl2 Zusammenfassung: Es wird eine Methode zur selektiven Fällung von VLDL im Blutserum mittels Phosphor-wolframsäure/MgCb beschrieben. Die Methode erlaubt die Ermittlung von LDL-Apolipoprotein B sowie di