Introduction: Dehydration can have an immediate negative impact on the performance of Soldiers intraining or combat environments. Field expedient methods for assessing hydration status may be valuable for servicemembers. Measurement of urine-specific gravity (USG) via refractometer is inexpensive, simple, fast, and a validatedindicator of hydration status. Manual (MAN) and digital (DIG) refractometers are commonly used in laboratory settings however, digital (DIG) devices have not been validated in the field against MAN devices. The purpose of thisstudy was to determine the validity and feasibility of using a DIG refractometer to assess USG compared to a MANrefractometer during a military field training exercise. Materials and Methods: Fifty-six military service members provided 672 urine samples during two 10-day field training exercises in central Texas. USG was assessed using a MANand a DIG refractometer with cutoff value of =1.020 indicating hypohydration. The study received a non-humanresearch determination. Results: The MAN measurements were strongly correlated with the DIG (r = 0.91, p <0.0001) measurements. Bland-Altman analysis demonstrated agreement between the refractometers. The DIG displayedgood sensitivity (93.9%) and specificity (85.8%) compared to the MAN. Conclusion: The DIG refractometer used inthis study was reliable and valid compared with a MAN device and was feasible for use in a field environment; however, the DIG refractometer tended to over overestimate hypohydration.
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Jeffery Heileson, L., & Julianna Jayne, M. (2019). Validity of digital and manual refractometers for measuring urine specific gravity during field operations: A brief report. Military Medicine, 184(11–12), e632–e636. https://doi.org/10.1093/milmed/usz082