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Disease Markers
Volume 2017, Article ID 2697464, 11 pages
Research Article

Within-Subject Reliability and between-Subject Variability of Oxidative Stress Markers in Saliva of Healthy Subjects: A Longitudinal Pilot Study

1Department of Removable Prosthodontics, School of Dental Medicine, University of Zagreb, Zagreb, Croatia
2Department of Laboratory Diagnostics, University Hospital Centre Zagreb, Zagreb, Croatia
3Department of Physiology, School of Dental Medicine, University of Zagreb, Zagreb, Croatia
4Department of Oral Medicine, School of Dental Medicine, University of Zagreb, Zagreb, Croatia
5Department of Dentistry, University Hospital Centre Zagreb, Zagreb, Croatia

Correspondence should be addressed to Iva Z. Alajbeg; rh.gzfs@gebjalai

Received 23 June 2017; Revised 1 October 2017; Accepted 11 October 2017; Published 15 November 2017

Academic Editor: Fabrizia Bamonti

Copyright © 2017 Iva Z. Alajbeg et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The present study evaluated diurnal variations and day-to-day fluctuations of salivary oxidative stress (OS) markers in healthy adult individuals. Whole unstimulated saliva was collected at 2 time intervals over 3 consecutive days. Glutathione peroxidase (GPX), superoxide dismutase (SOD), total antioxidant capacity (TAC), and uric acid (UA) were analyzed using spectrophotometric methods, while 8-hydroxydeoxyguanosine (8-OHdG) and malondialdehyde (MDA) were determined using immunoassays. No significant differences for salivary OS markers between men and women were observed. For all examined OS markers, no significant day-to-day variations were demonstrated. Significant diurnal variations were found in salivary GPX, TAC and MDA levels. For SOD, TAC, GPX, and UA, good-to-moderate intraindividual coefficients of variations (CVs) were observed in more than 75% of the subjects. For MDA and 8-OHdG, intraindividual CVs > 35% were observed in 60% and 40% of the subjects, respectively. Between-subject variance was wide for all examined OS markers (CV% 30.08%–85.70%). Due to high intraindividual variability in the salivary concentrations of MDA and 8-OHdG, those markers cannot be reliably verified based on single measurements and multiple measurements over several days would provide more reliable information. Salivary SOD, TAC, GPX, and UA proved stable across three days of measurement. Trial Registration. NCT03029494. Registered on 2017-01-19.