Paraoxonase-1 Enzyme Activity Assay for Clinical Samples: Validation and Correlation Studies

Background: Paraoxonase-1 (PON1) enzyme is reported in various types of tissues and linked to numerous pathophysiological disorders. It is a potential biomarker in many pathological conditions such as cardiovascular diseases.
Material and Methods: We conducted several small-scale studies to evaluate PON1 performance as affected by sample types, storage, and interferences. We also carried out short-term studies to compare the performance of the widely used PON1 assay to the similar commercially available PON1 kit assay method; sample size for the method comparison was N=40, and the number varied for other validation experiments.
Results: Our studies using various types of anticoagulants show that samples collected in tubes with NaF, citrate, EDTA, clot activator, and sodium heparin have increased PON1 levels that are 49%, 24.5%, 19.8%, 11.4%, and 8%, respectively, higher compared to serum samples collected in plain tubes. However, samples collected in lithium heparin tubes demonstrated 10.4% lower PON1 levels compared to serum collected in plain tubes. Biological interference such as hemolysis has little effect on PON1 levels; however, samples spiked with lipids have shown 13% lower PON 1 levels. Our studies comparing the PON1 method commonly available for PON1 assay and a similar non-ELISA commercially available PON1 kit method showed a weak Spearman correlation coefficient of R2=0.40 for the range of 104.9–245.6 U/L.
Conclusions: The current study provides new validation data on enzyme PON1 performance. While no appreciable change was seen with storage, samples type affects the enzyme performance. Our results should encourage additional clinical studies to investigate other aspects of factors known to affect PON1 enzyme function and performance.

Keywords: Anticoagulants - pharmacology, Adult, Aryldialkylphosphatase - metabolism, Enzyme Assays - methods, Enzyme-Linked Immunosorbent Assay, Hemolysis - drug effects, Reproducibility of Results, Statistics, Nonparametric