Determination of LDL cholesterol and LDL apolipoprotein B following precipitation of VLDL in blood serum with phosphotungstic acid/MgCl2.
A method is described for the selective precipitation of VLDL in blood serum using phosphotungstic acid/MgCl2. The method allows for the calculation of LDL apolipoprotein B as well as for the calculation of LDL cholesterol (following the additional determination of HDL cholesterol). Dependent on the triglyceride and the cholesterol content of the serum, three different procedures were developed using phosphotungstic acid and MgCl2 in different concentrations in the precipitation assay. Within the tested range of 3-10 mmol/l total cholesterol and 1-4 mmol/l 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/MgCl2 (= serum cholesterol - LDL cholesterol), and the cholesterol values obtained by ultracentrifugation (d greater than 1.006 kg/l) revealed a good measure of agreement (r = 0.97, y = 0.93 X + 0.35, n = 76). An equally good measure of agreement was found for the corresponding apolipoprotein B values (r = 0.96, y = 1.03 X - 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.
D001053:Apolipoproteins / Q000097:blood*; D001055:Apolipoproteins B; D011232:Chemical Precipitation; D002784:Cholesterol / Q000097:blood*; D008078:Cholesterol, LDL; D006801:Humans; D008055:Lipids / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood*; D008079:Lipoproteins, VLDL / Q000097:blood*; D008274:Magnesium; D015636:Magnesium Chloride; D010772:Phosphotungstic Acid; D011786:Quality Control; D014280:Triglycerides / Q000097:blood; D014461:Ultracentrifugation
D001053:Apolipoproteins; D001055:Apolipoproteins B; D008078:Cholesterol, LDL; D008055:Lipids; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D014280:Triglycerides; D015636:Magnesium Chloride; D010772:Phosphotungstic Acid; D002784:Cholesterol; D008274:Magnesium