Use of a dual-precipitation procedure for measuring high-density lipoprotein 3 (HDL3) in normolipidemic serum.

We compared results by a dual-precipitation method (J Lipid Res 1982;23:1206-23) for measuring high-density lipoprotein 3 (HDL3) cholesterol with those by ultracentrifugation at d 1.125, using 56 fresh and 105 frozen-stored serum samples. For both methods, HDL2-cholesterol was calculated as the difference between total HDL-cholesterol and HDL3-cholesterol. In general, for pooled serum samples, agreement was closest with ultracentrifugation when we used a dextran sulfate concentration of 5.0 mg/L to precipitate the HDL2-rich fraction, although the optimal concentration varied from 3.0 to 6.8 mg/L for different pools. For individual samples, the values for HDL3 by dual precipitation averaged 12.8% lower than by ultracentrifugation. The coefficients of correlation between the two methods were HDL3, r = 0.70; and HDL2, r = 0.92. The dual-precipitation method reflected the expected sex-related differences in HDL2-cholesterol concentration and inverse relationship with triglyceride concentration.