Interference of blood clotting factors in the determination of HDL2- and HDL3-cholesterol by the dual precipitation method.

Previously we found that in the dual precipitation method for determination of HDL2- and HDL3-cholesterol the optimal concentration of dextran sulfate was 0.87 g/l instead of 1.3 or 1.5 g/l. In the present study, we performed the dual precipitation method both in serum and in EDTA-plasma samples in order to investigate whether the method is sensitive for plasma-serum differences. It was found, that in the analysis of EDTA-plasma samples a twice higher final concentration of dextran sulfate was needed. Addition of the dextran sulfate resulted in the appearance of fibrin structures in the HDL-fraction which may have diminished the effective dextran sulfate concentration in the precipitation reaction. Although the use of plasma is advised in the analysis of lipoproteins, the use of EDTA-plasma in precipitation methods for determination of HDL-cholesterol and its subfractions cannot be recommended.