Objective: HDL is considered as anti-atherogenic and it exerts this effect with reverse cholesterol transport and with the contribution of enzymes such as paraoxonase and platelet activating factor acetylhydrolase. Data on biological variation can be used to determine the quality specifications of a method, the utility of the reference values for the method and the magnitude of change that is significant and related to disease. In the light of this information, the aim of the study was to determine the biological variations of paraoxonase and HDL-cholesterol, the influence of biological variation of HDL-C on paraoxonase and with the obtained data to determine the quality specifications of the methods.

Materials and Methods: Blood was obtained from 17 subjects on days 0, 1, 2, 7, 14, 21 and 28. After all the analyses were completed intra-individual and inter-individual biological variations, index of individuality and quality specifications were computed.

Results: Intra-individual, inter-individual biological variations for paraoxonase and HDL-C were 11.45%, 70.83% and 6.24%, 28.73%, respectively. For both of the analytes the index of individuality was <0.6. Quality specifications for paraoxonase were as follows: imprecision < 5.73%, bias <17.71% and total allowable error <27.16%.

Conclusion: Inter-individual biological variation of paraoxonase was high and the genetic factors are the main determinants of this variation. Meanwhile parameters of lipid metabolism, smoking, aging and diet also contribute to this variation. Since biological variation of HDL-C was relatively low, its effect on biological variation of paraoxonase was limited. Due to low index of individuality it seems more relevant to interpret the results of both parameters according to the previous results of the individual instead of the population based reference values.