773 EP095 – Comparison of saliva osmolarity to urine specific gravity to assess hydration status in a collegiate football setting

Background Hydration status is one measure used to determine risk of heat illness, such as heat stroke. The most common assessment used is urine specific gravity. However, this test presents inherent challenges regarding specimen collection and analysis. Saliva osmolarity is a new assessment that could eliminate many of the challenges experienced with urine specific gravity testing. Objective To determine the diagnostic accuracy and test-retest reliability of saliva osmolarity compared to urine specific gravity within an athletic patient population. Design Prospective, Cross-sectional Setting Collegiate, American football athletic training facility Participants To assess diagnostic accuracy, 16 male American football players were recruited. Reliability testing had a separate sample of 13 male football players recruited for data collection. Interventions Urine specific gravity and saliva osmolarity were measured before and following practice sessions over a six-day period and pooled into a single data set. Saliva osmolarity test-retest reliability was performed over a single data collection. Main Outcome Measures All urine specific gravity and saliva osmolarity data were dichotomized into a 2x2 contingency table based upon published standards and manufacturer guidelines indicating hydrated or not hydrated status. Reliability of saliva osmolarity values in a test-retest format was assessed using an intraclass correlation coefficient (ICC 2,1). Results Saliva osmolarity percent accuracy was 41.6%, sensitivity was 78.6%, and specificity was 19.7%. The positive predictive value was 36.7% and the negative predictive value was 60.9%. Test-retest data found an ICC 2,1 value of 0.573 with a 95% confidence interval of 0.843 to 0.099 (F(12,12)=4.104, p=0.011). Conclusions Compared to urine specific gravity testing, the saliva osmolarity measurement had low overall diagnostic accuracy with poor to moderate test-retest reliability. In this sample saliva osmolarity testing did not accurately assess hydration status. Given the significant testing advantages saliva osmolarity testing has over traditional urine specific gravity further investigation is needed.