Salivary Amylase And Iga As A Measure Of Dehydration

Abstract

PURPOSE: Blood and urine tests are used to measure hydration status, but there is no accepted tool to rapidly assess dehydration. It has been shown that saliva amylase concentration goes up and that IgA levels decrease during periods of mild dehydration. The purpose of this study was to investigate the ability of a saliva probe (HydraDx), specifically measuring salivary amylase and IgA, to reliably assess changes of hydration status when compared to standard clinical measurements of dehydration. METHODS: Twenty participants (10 male and 10 female) were recruited for a 4 day protocol. The first three days body weight (BW), urine specific gravity (USG), salivary amylase, salivary IgA were collected to determine baseline hydration status. The fourth day participants completed a 90-minute exercise protocol on a treadmill with a goal of achieving a body weight loss of 1.5% or greater. Hydration during exercise was prohibited. Every 30 minutes body weight, salivary amylase, and salivary IgA were recorded. Prior to and after exercise USG, urine osmolality (OSM), serum creatinine (Cr), and hematocrit (HCT) were measured. RESULTS: Subjects lost an average of 1.89% body weight. Urine markers of dehydration showed that 100% of subjects increased USG and OSM. Blood markers of dehydration showed that 87% of subjects increased Cr and HCT. The amylase:IgA ratio showed a significant increase when pre-exercise and post-exercise levels were compared (Pre 1.73 ± 1.39 vs Post 7.94 ± 7.37; p = 0.008) with 87% of subjects increasing the saliva amylase:IgA ratio. There did not appear to be a correlation between the percent body weight loss and change in amylase:IgA ratio (r = 0.101; p = 0.743). CONCLUSIONS: The salivary amylase and IgA ratio may be a quick and novel marker of dehydration. All hydration assessment techniques evaluate a complex fluid matrix and interconnected fluid compartments and no single technique has yet been proven to be the gold standard. There is a need to develop field hydration assessment techniques that have excellent precision, accuracy, reliability, portable, inexpensive, that are safe and simple to use.