Quantification of lipoprotein cholesterol in serum from children with different lipoprotein profiles: heparin-calcium precipitation and ultracentrifugation compared.

We compared the serum lipoprotein cholesterol concentrations in subgroups of children (n = 360), ages 5-17 years, as measured by the heparin-Ca2+ and preparative ultracentrifugation methods. Children were grouped from the total population on the basis of their previous results for serum beta- and pre-beta-lipoprotein cholesterol (Group I: low beta- and low pre-beta-; Group II: high beta- and low pre-beta; Group III: high beta- and high pre-beta-; Group IV: low beta- and high pre-beta-). The values for very-low-density (VLDL) cholesterol by ultracentrifugation method were 44, 53, 15, and 10 mg/L greater than the values for pre-beta-lipoprotein cholesterol by the heparin-Ca2+ method in Groups I, II, III, and IV, respectively; the differences were not significant in Group IV. The values of low-density (LDL) cholesterol were 64, 137, 144, and 73 mg/L less than the values for beta-lipoprotein cholesterol in Groups I, II, III, and IV, respectively (p less than 0.005). On the other hand, high-density (HDL) cholesterol concentrations in the respective four groups were 10, 37, 93, and 52 mg/L greater than alpha-lipoprotein cholesterol concentrations; the differences were significant for Groups II, III, and IV (p less than 0.005). Overall, the values for LDL-cholesterol correlated highly with beta-lipoprotein cholesterol (r = 0.94), whereas correlations for VLDL- and HDL-cholesterol values with pre-beta-lipoprotein cholesterol (r = 0.76) and alpha-lipoprotein cholesterol (r = 0.77) were somewhat lower. The differences between these two methods may result from their different operational definitions for measuring serum lipoproteins and the possibility that without appropriate corrections the values obtained by preparative ultracentrifugation do not serve as reference values.