Precipitation of LDL with sulphopolyanions: a comparison of two methods for LDL cholesterol determination

Two commercially available tests for the determination of LDL cholesterol were compared. The determination principle lies in the precipitation of LDL using heparin (Merck, Darmstadt test) or using polycyclic surface activated anions (bioMérieux test), as well as ascertaining LDL cholesterol by subtracting cholesterol in the supernatant from total cholesterol (Merck, Darmstadt test) or the direct determination of cholesterol in the redissolved precipitate (bioMérieux test). Regression analysis of the LDL cholesterol values obtained by precipitation and the LDL cholesterol values obtained by the combination of ultracentrifugation and HDL cholesterol determination (cholesterol in the d greater than 1.006 kg/l ultracentrifugation fraction- HDL cholesterol) resulted in a good correlation (precipitation using polycyclic surface activated anions: r = 0.95, y = 1.01x - 0.14, n = 34; heparin precipitation: r = 0.94, y = 0.86x + 0.10, n = 28). In sera containing triglycerides ranging from 2.28 mmol/l to 10.9 mmol/l there was an adequate agreement between the values obtained by precipitation with polycyclic surface activated anions and those of the reference method (r = 0.94, y = 0.9x + 0.47, n = 51), whereas the data obtained by heparin precipitation clearly deviated from the data of the reference method (r = 0.69, y = 0.75x + 0.003, n = 32).