Adams JD et al. 2021
Combining urine color and void number to assess hydration in adults and children
To evaluate the diagnostic ability of two combined practical markers for elevated urine osmolality (underhydration) in free-living adults and children.
One hundred and one healthy adults (females n=52, 40±14 y, 1.70±0.95 m, 76.7±17.4 kg, 26.5±5.5 kg/m2) and 210 children (females=105, 1.49±0.13 m, 43.4±12.6 kg, 19.2±3.2 kg·m-2) collected urine for 24-h. Urine was analyzed for urine osmolality (UOsm), color (UC), while the number of voids (void) was also recorded. Receiver Operating Characteristic (ROC) analysis was performed for UC, void, and combination of UC and void, to determine markers’ diagnostic ability for detecting underhydration based on elevated UOsm (UOsm ≥800 mmol·kg-1).
Linear regression analysis revealed that UC was significantly associated with UOsm in both adults (R2=0.38; P<0.001) and children (R2=0.45; P<0.001). Additionally, void was significantly associated with UOsm in both adults (R2=0.13; P<0.001) and children (R2=0.15; P<0.001). In adults, when UC>3 and void <7 were combined, the overall diagnostic ability for underhydration was 97% with sensitivity and specificity of 100% and 88%, respectively. In children, UC >3 and void <5 had an overall diagnostic ability for underhydration of 89% with sensitivity and specificity of 100% and 62%, respectively.
Urine color alone and the combination of urine color with void number can a valid and simple field-measure to detect underhydration based on elevated urine osmolality.
A word from our expert: Dr Erica Perrier, Head of the Health and Hydration Science Team, Danone Research France:
“People need easy methods to monitor hydration in their daily lives. Previously, both urine color, and counting the number of voids, have been shown to be good proxies of hydration. This study finds that combining urine color and number of voids is an accurate way of detecting underhydration in adults and children. Specifically, in adults, a darker urine color (4 or higher on the eight-color urine color scale published by Armstrong et al.); combined with less that 7 voids in 24h, accurately predicts underhydration. In children, a urine color of 4 or darker, combined with less than 5 voids in 24h, accurately predicts underhydration.”