[The effect of freezing-thawing of human blood serum on the results of the determination of high density lipoprotein cholesterol].

The effect of repeated freezing-defreezing of the serum on the values of high density lipoprotein cholesterol measured by Abel's method was studied. Mixtures for the precipitation of lipoproteins were as follows: heparin + Mn2+, dextran sulfate + Mg2+, phosphotungstic acid + Mg2+, and polyethylene glycol. Variations in the measured cholesterol values were insignificant. Statistically reliable results (p less than 0.05) were obtained only with polyethylene glycol, with the variations not surpassing 3%.