Effects of Agitation and Storage Temperature on Measurements of Hydration Status

BACKGROUND: Hypohydration can have significant implications on normal physiological functions of the body. OBJECTIVES: This study aimed to determine the impact of agitation, storage temperature, and storage time on urine osmolality compared to the criterion control. PATIENTS AND METHODS: We used a descriptive diagnostic validity test design. To investigate agitation, we recruited 75 healthy individuals (males = 41, females = 34; mean age = 22 ± 5 years; mean self-reported height = 172 ± 23 cm and mass = 77 ± 17 kg) who provided one or more samples (total = 81). The independent variables were agitation (vortex, hand shaken, no agitation) and temperature (room temperature, freezer, and refrigerator) type. Participants completed informed consent, a health questionnaire and were asked to provide a urine sample, which was split and labeled according to agitation type or storage temperature. Urine osmolality was used to determine hydration status at two time points (within 2 hours [control], 48 hours). We used t-tests to determine the difference between each condition and the control and calculated percent error for each condition. RESULTS: No significant differences for no agitation (t(79) = -0.079, P = 0.937), hand shaken (t(79) = 1.395, P = 0.167) or vortex mixed (t(79) = -0.753, P = 0.453) were identified when compared to the criterion control. No significant differences for room temperature (t(82) = -0.720, P = 0.474), refrigerator (t(82) = -2.697, P = 0.008) or freezer (t(82) = 2.576, P = 0.012) were identified when compared to the criterion control. CONCLUSIONS: Our findings suggest agitation of urine specimen is not necessary and samples do not require refrigeration or freezing if assessed within 48 hours. Analysis within two hours of collection is not necessary and samples can be stored for up to 48 hours without impacting the hydration status of the sample.