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. 2024 Apr 14;131(7):1181-1188.
doi: 10.1017/S000711452300274X. Epub 2023 Nov 28.

The weight, urine colour and thirst Venn diagram is an accurate tool compared with urinary and blood markers for hydration assessment at morning and afternoon timepoints in euhydrated and free-living individuals

Marcos S Keefe  1 , Hui-Ying Luk  2 , Jan-Joseph S Rolloque  1 , Nigel C Jiwan  2 , Tyler B McCollum  1 , Yasuki Sekiguchi  1
Affiliations

The weight, urine colour and thirst Venn diagram is an accurate tool compared with urinary and blood markers for hydration assessment at morning and afternoon timepoints in euhydrated and free-living individuals

Marcos S Keefe et al. Br J Nutr. .

Abstract

The weight, urine colour and thirst (WUT) Venn diagram is a practical hydration assessment tool; however, it has only been investigated during first-morning. This study investigated accuracy of the WUT Venn diagram at morning and afternoon timepoints compared with blood and urine markers. Twelve men (21 ± 2 years; 81·0 ± 15·9 kg) and twelve women (22 ± 3 years; 68·8 ± 15·2 kg) completed the study. Body mass, urine colour, urine specific gravity (USG), urine osmolality (UOSM), thirst and plasma osmolality (POSM) were collected at first-morning and afternoon for 3 consecutive days in free-living (FL) and euhydrated states. Number of markers indicating dehydration levels were categorised into either 3, 2, 1 or 0 WUT markers. Receiver operating characteristics analysis calculated the sensitivity and specificity of 1, 2 or 3 hydration markers in detecting dehydration or euhydration. Specificity values across morning and afternoon exhibited high diagnostic accuracy for USG (0·890-1·000), UOSM (0·869-1·000) and POSM (0·787-0·990) when 2 and 3 WUT markers were met. Sensitivity values across both timepoints exhibited high diagnostic accuracy for USG (0·826-0·941) and UOSM (0·826-0·941), but not POSM in the afternoon (0·324) when 0 and 1 WUT markers were met. The WUT Venn diagram is accurate in detecting dehydration for WUT2 and WUT3 based off USG, UOSM and POSM during first-morning and afternoon. Applied medical, sport and occupational practitioners can use this tool in field settings for hydration assessment not only at various timepoints throughout the day but also in FL individuals.

Keywords: Dehydration; Field settings; Hydration assessment.

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Figures

Fig. 1.
Fig. 1.
Experimental design timeline. Participants visited the laboratory in the morning and afternoon in a free-living condition for the first 3 d (Days 1–3). Following a 1-d break (Day 4), participants performed the remaining visits (Days 5–7) in a euhydrated condition (defined by a urine spot sample of USG < 1·020). Each visit consisted of attainment of a urine spot sample, blood sample, nude body mass measurement and thirst level.
Fig. 2.
Fig. 2.
Morning (M) and afternoon (A) urine specific gravity, urine osmolality and plasma osmolality when weight, urine colour and thirst (WUT) Venn diagram criteria were used to determine hydration status. Data groups are split into morning and afternoon experimental conditions of free-living (FL) and euhydrated (EUH).
Fig. 3.
Fig. 3.
Receiver operating characteristic (ROC) curves from morning and afternoon timepoints for (a) urine specific gravity, (b) urine osmolality and (c) plasma osmolality. WUT1, WUT2 and WUT3 thresholds are plotted appropriately.
Fig. 4.
Fig. 4.
Receiver operating characteristic (ROC) curves from morning and afternoon timepoints for the free-living (FL) condition (a) urine specific gravity, (b) urine osmolality and (c) plasma osmolality. WUT1, WUT2 and WUT3 thresholds are plotted appropriately.
Fig. 5.
Fig. 5.
Weight, urine colour and thirst (WUT) Venn diagram is accurate for detecting dehydration at both morning and afternoon timepoints when two (WUT2) or three (WUT3) WUT variables are met in comparison to hydration indices of plasma osmolality, urine osmolality and urine specific gravity (USG). Created with BioRender.com.
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