Salivary biomarkers of inflammation and oxidative stress in healthy adults.

OBJECTIVES

Diagnostic value of saliva depends on the reproducibility of data in repeatedly collected samples and predictable correlations between saliva and blood. We aimed to investigate the reliability, blood reflectance, and influence of blood contamination in the analysis of inflammatory and oxidative stress biomarkers in saliva samples.

DESIGN

In total, 37 healthy young male participants (26.7 ± 2.2 years) were included. Unstimulated whole saliva and blood samples were collected on the first visit, and saliva samples were collected again after 2-3 days. The concentrations of total protein and inflammatory [C-reactive protein (CRP), IL-1β, IL-6, and TNF-α] and oxidative stress [8-hydroxy-2'-deoxyguanosine (8-OHdG), malondialdehyde (MDA), and total antioxidant capacity (TAC)] biomarkers in saliva and blood, and as well as blood contamination biomarkers (transferrin and hemoglobin) in saliva were analyzed.

RESULTS

The intra-class correlations of all examined biomarkers except TNF-α were fair to excellent. Significant positive correlations between CRP and IL-6 and between total protein and TAC were stable in the saliva samples collected on different days. Notably, IL-6 was the only biomarker that showed a significant correlation between saliva and blood. As the concentration of salivary transferrin increased, the saliva/blood ratios of total protein and TAC also increased. The concentration of salivary hemoglobin did not affect the saliva/blood ratios of biomarkers.

CONCLUSIONS

The findings of this study are limited to healthy young males. For clinical applications, studies on salivary diagnostics should be performed for individual disease and health conditions, demographic characteristics, and biomarkers.