Variability of Salivary Oxidative Stress Markers in Healthy Subjects
Objectives: Little data exist regarding normal variations for salivary oxidative stress (OS) markers in healthy population. The aim of this study was to determine the normal intra- and inter-day variations of salivary OS markers in healthy adult individuals.
Methods: Unstimulated saliva from 15 healthy adults was collected twice daily (7:00 AM and 5:00 PM) on three consecutive days. Salivary levels of OS markers, including glutathione peroxidase (GPX), superoxide dismutase (SOD), total antioxidant capacity (TAC), 8-hydroxydeoxyguanosine (8-0HdG) and uric acid (UA) were determined.
Results: Concentrations of most measured markers did not differ significantly during the day; only SOD showed significant intra-day variations, with significantly higher values in the morning compared to the afternoon measurements (F=12.72, p=0.003). A within subjects MANOVA did not show the significant influence of “sampling day” as a factor affecting the variability of salivary OS markers (P>0.05). The highest intraclass correlations (ICC’s) were obtained for UA and 8-0HdG (0.871 and 0.858 respectively).
Conclusions: Salivary OS markers can be measured reproducibly over time, since no significant inter-day variability for all measured markers was observed. Moreover, concentrations of most measured markers did not differ significantly during the day. Only SOD showed significant intra-day variations. The excellent reliability obtained for UA and 8-0HdG indicates that those markers could potentially be more specific in terms of distinguishing patient population from the healthy controls.