Serum paraoxonase 1 activity in dogs: preanalytical and analytical factors and correlation with C‐reactive protein and alpha‐2‐globulin

Background Serum activity of paraoxonase ( PON 1) decreases during inflammation in many species. Little information is available on paraoxon‐based tests and the possible role of PON 1 in dogs. Objectives The objectives of the study were to validate an automated paraoxon‐based assay to measure PON 1 activity in canine serum, to determine its stability under different storage conditions, to determine a reference interval ( RI ) in healthy dogs, and to assess whether PON 1 is of comparable diagnostic value as C‐reactive protein ( CRP ) and α 2 ‐globulins. Methods Intra‐assay and inter‐assay imprecision, linearity under dilution ( LUD ), interference, and storage artifacts were evaluated. A PON 1 RI was determined for healthy dogs, and PON 1 activity, sensitivity, and specificity were compared with CRP and α 2 ‐globulins. Results Intra‐ and inter‐assay CV s were below 1.6% and 7.8%, respectively. The LUD test fitted the linear model. PON 1 activity measurements were increased after addition of hemolysates and lipids, and after storage for 12 hours at room temperature, 72 hours at 4°C, and 6 months at −20°C. PON 1 activity and CRP or α 2 ‐globulins did not correlate well. PON 1 activity decreased significantly only in dogs with very high CRP concentrations. In contrast to CRP and α 2 ‐globulins, PON 1 activity was not significantly different between dogs with and without inflammation. Conclusions The automated paraoxon‐based method to assess serum canine PON 1 activity was accurate and precise, but it was influenced by hemolysis, lipemia, and standard storage conditions. In this study, contrarily to CRP and α 2 ‐globulins, PON 1 activity did not provide diagnostic value as a negative acute phase protein in dogs.