Abstract
BACKGROUND: Mounting evidence suggests that malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) are valuable biomarkers of lipid and nucleic acid oxidation in numerous canine diseases. However, their application in clinical settings is limited due to the absence of reference intervals (RI) and the analytical inconsistencies. Therefore, this study aimed to characterize serum MDA and 8-OHdG concentrations in dogs, to establish assay-specific RI, and to identify biological, haematological and biochemical factors influencing these markers. METHODS: A total of 190 clinically healthy dogs were recruited, including pet dogs, working dogs and shelter dogs. Serum MDA concentration was measured by the Thiobarbituric Acid Reactive Substances (TBARS) assay, while 8-OHdG levels were determined by using a competitive ELISA. RI were established by non-parametric methods. Potential associations between oxidative stress (OS) biomarkers and multiple biological, haematological and biochemical factors were assessed using multivariate regression models. RESULTS: RI for serum MDA (1.85-14.51 µM) and 8-OHdG (0.06-0.75 ng/mL) were established in the reference population (144 and 143 dogs, respectively). The multivariate regression model for MDA revealed a positive association with total cholesterol concentration, and a negative association with monocyte count. 8-OHdG level was positively associated with urea concentration. Notably, both models also revealed a significant association between MDA and 8-OHdG. Biological factors, including the age and size of the animals, did not exert a significant influence on the results. CONCLUSIONS: This is the first study to establish serum RI for MDA and 8-OHdG in a large and diverse canine population. Additionally, the multivariate regression models identified relevant haematological and biochemical, but not biological factors that should be considered when interpreting the results. These findings could significantly enhance the application of MDA and 8-OHdG as biomarkers in clinical settings, and promote further exploration of their value in canine diseases.