Variability of Saliva Viscosity - Potential Impact

Abstract

As novel COVID-19 testing develops, saliva has become of increasing interest as an alternate biological sample for rapid testing. The appeal in saliva-based testing lies within the ease of which samples are collected, as well as patient comfort throughout the collection process. With this, it has become increasingly important to delineate the characteristics of saliva viscosity due to its effects on the movement and interactions of the substances and molecules found within it. The characteristics that affect saliva viscosity include the presence of aggregates, variations in temperature, and time elapsed between sample collection and testing. Understanding how physicochemical properties and temperature affect saliva’s viscosity are important in generating guidelines for proper sample handling in saliva testing to ensure consistent and reliable results. In this study, passive sampling of saliva was analyzed. This type of collection ensures a more uniform saliva composition, suggesting that variations in viscosity can be attributed solely to modifications in saliva handling post-collection. The data suggested that saliva viscosity is greatest immediately following collection of the saliva sample, increases with higher quantities of aggregates in saliva, and decreases tremendously when the sample has been frozen and thawed to room temperature. These findings suggest that to ensure accuracy and uniformity in quantitative saliva-based test results, protocols should favor the testing of a sample immediately following its collection. The implications of these results in optimizing saliva testing are far reaching. The value of saliva based testing extends far beyond COVID-19 or other disease testing. It is also gaining utility in understanding daily fluctuations in hydration state and in other wellness applications.