Saliva Test Could Help Diagnose Plaque Psoriasis, Study Suggests

Total oxidative stress and oxidative stress index values in the saliva may be useful as a diagnostic biomarker for plaque psoriasis, according to new research.

A team of scientists from the Medical University of Bialystok, in Poland, wanted to generate useful biomarkers to diagnose plaque psoriasis by examining the redox balance parameters and oxidative stress in the saliva and blood of patients.

To do so, the investigators recruited 40 healthy adult patients and 40 patients with plaque psoriasis. They decided to look at salivary parameters in addition to blood, in part because saliva is easier to collect, causes lower anxiety in patients and has the potential to make it easier for patients to monitor their own health.

Salivary redox balance has been found to be a useful biomarker in a number of diseases, but until this study no one had tried evaluating it as a tool for diagnosing psoriasis patients.

After testing the 80 patients in the study, a number of statistically significant differences were clear.

“We... demonstrated that plaque psoriasis disturbs enzymatic antioxidant systems in saliva and leads to oxidative damage to salivary proteins and lipids,” writes Anna Skutnik-Radziszewska, a doctoral student at the university, and the study’s corresponding author. “We observed that intensification of oxidative modifications of proteins and lipids in saliva correlated with the disease duration.”

The results were published last month in Oxidative Medicine and Cellular Longevity. Specifically, Skutnik-Radziszewska and colleagues found:

• The concentration of salivary peroxidase, catalase, and superoxide dismutase was significantly higher in the unstimulated saliva of patients with plaque psoriasis versus healthy subjects.
• Salivary peroxidase and catalase were higher in the stimulated saliva of psoriatic patients.
• In erythrocytes of patients with plaque psoriasis, the concentration of glutathione peroxidase and catalase were significantly higher than controls.
• Levels of advanced oxidation protein products, advanced glycation end products, malondialdehyde, and total lipid hydroperoxide were notably higher in both the stimulated and unstimulated saliva of the psoriasis group, as well as in the plasma.
• The concentration of total protein and salivary amylase was significantly lower in the unstimulated and stimulated saliva of psoriatic patients compared to the healthy control.
• In patients with plaque psoriasis, redox imbalances correlated with the prevalence of oxidation reactions.
• Mechanisms related to the synthesis and secretion of proteins and the activity of amylase were lower in both the parotid and submandibular glands of psoriatic patients, though the inhibition was greater in the former.

Taken together, the investigators found that saliva can be a highly meaningful diagnostic avenue in psoriasis.

“The fact is not surprising as the concentration of numerous substances in saliva correlates with their content in the blood serum, and saliva is a noninvasive, noninfectious, and relatively stable laboratory material,” they write.

However, they argue that total oxidative stress (TOS) and oxidative stress index (OSI) value are particularly notable metrics.

“The diagnostic value of TOS and OSI is also emphasized by the positive correlation between the disease duration as well as [psoriasis area and severity index] and the content of TOS and OSI in [unstimulated saliva] and plasma,” they write.

TOS and OSI are therefore potentially strong biomarkers for psoriasis, they conclude.

Reference

Skutnik-Radziszewska A, Maciejczyk M, Fejfer K, et al. Salivary antioxidants and oxidative stress in psoriatic patients: Can salivary total oxidant status and oxidative status index be a plaque psoriasis biomarker [published online January 3, 2020]. Oxid Med Cell Longev. doi:10.1155/2020/9086024.