The measurement of the lactonase activity of paraoxonase-1 in the clinical evaluation of patients with chronic liver impairment

Aims: We investigated the analytical performance of a new assay of the lactonase activity of paraoxonase-1 and its efficacy in the assessment of liver damage. Design and methods: Serum lactonase activity was determined by the hydrolysis of 5-thiobutyl butyrolactone in 633 healthy individuals and 369 patients with chronic liver disease. Paraoxonase-1, 2, and 3 gene polymorphisms were analyzed by the MassArray (TM) method. Results: Linearity was up to 10 U/L. Detection limit was 0.12 U/L. Imprecision was <= 17.7%. Lactonase values in our normal population were 5.99 (3.29-13.61) U/L. Lactonase activity showed a lower influence of genetic polymorphisms than the classical assay using paraoxon. Both measurements showed a similar efficiency in testing for liver dysfunction. Conclusion: We report a reliable assay using a non-toxic substrate for the measurement of serum lactonase activity. The influence of genetic variability is low. The assay could be a useful addition to tests evaluating liver impairment. (C) 2008 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.