Electrophoretic fractionations of lipoproteins in dogs: Intra- and inter-assay imprecision and effects of different storage conditions.

Background: Lipoprotein fractions are reported to be unstable in stored human samples, and there is a paucity of information on the analytical precision of electrophoretic separation of lipoproteins in canine serum samples.

Objective: The aim of this study was to assess the effects of intra- and inter-assay imprecision and of storage conditions on the electrophoretic separation of canine lipoproteins.

Methods: Imprecision was assessed by calculating the coefficient of variation (CV) of five replicates of six serum samples run in two sequential runs of agarose gel lipoprotein electrophoresis. The effect of storage was assessed with a Friedmann test by comparing the results of samples analyzed after sampling (T0) and after 24 and 48 h at room temperature or stored at 4°C and after 7, 14, 21 days, 1, 2, and 3 months at -20°C or at -80°C. Moreover, electrophoretograms obtained after storage were visually analyzed by two observers in a blind manner to assess whether storage alters the electrophoretic profile.

Results: The imprecision of high-density lipoproteins (HDL), low-density lipoproteins (LDL), very low-density lipoprotein (VLDL), and chylomicrons were respectively 0.8%-11.5%, 2.4%-22.7%, 2.3%-11.5%, and 12.5%-105.2%. Compared with T0, HDL significantly decreased, and LDL significantly increased over time in all the storage conditions, whereas VLDL significantly increased only in frozen samples, and chylomicrons did not significantly differ. In frozen samples, deviations from baseline values were lower than the imprecision of the method, and visual misclassifications of electrophoretograms were rare.

Conclusions: Despite minimal variation in the percentage of some fractions, freezing does not influence the interpretation of canine lipidograms.