A study of the use of polyethylene glycol in estimating cholesterol in high-density lipoprotein.

We studied polyethylene glycol 6000 precipitation of lipoproteins other than high-density lipoproteins, before cholesterol is estimated in the supernate. Other lipoproteins in the supernatant fractions were detected by using rocket immunoelectrophoresis. A polyethylene glycol concentration of 75 g/L in the final mixture appeared to be optimal, and results agreed with those obtained by ultracentrifugation. Differences in serum pH, use of polyethylene glycol from different suppliers, or the presence of ethylenediaminetetraacetate resulted in values that differed significantly (by 40 to 60 mumol/L) from the reference values. Polyethylene glycol did not interfere in four different methods for determination of cholesterol. In combination with an enzymic cholesterol method, the polyethylene glycol method appeared to be very precise, even when lipemic sera (triglycerides up to 5.5 mmol/L) were analyzed that had diminished high-density lipoprotein cholesterol values. We consider this method a method of choice, especially when lipemic sera are tested and enzymic cholesterol analysis is used.