A lavatory urine color (LUC) chart method can identify hypohydration in a physically active population

Purpose: To provide a new and efficient at-the-toilet-bowl method of self-assessing urine concentration via urine color (Uc) to identify hypohydration. Methods: A large athletic population (n = 189) delivered a urine sample, then chose a color panel that was displayed on the back wall of the lavatory stall. Selection was based on duration of urine voiding time, so that for a short-duration, the lighter panel was selected; for a mid-duration, the mid color panel; and for a longer-void-duration, the darker panel was selected. Then, subjects noted if their urine was lighter than, similar to, or darker than the selected color panel. Trained investigators also rated subjects’ urine samples. To assess validity of Uc classification, the outcome was compared with a urine concentration (urine specific gravity, USG, and urine osmolality) threshold indicating hypohydration. Results: Urine color was scored similarly by subjects and investigators (P = 0.99). Based on receiver operating curves (ROC), the method scored fair, i.e., the area under the curve ranging 0.73–0.82, with an accuracy of participants and investigators correctly classifying 72% and 75% urine samples compared to a USG threshold of 1.020, respectively, and 62% and 70% compared to a urine osmolality threshold of 836 mmol·kg⁻¹, respectively. Conclusion: This new lavatory urine color (LUC) method of scoring Uc levels to assess potential hypohydration gives results similar to those of traditional urine color charts, but it has the advantage of an immediate assessment of hydration status based on scoring urine color directly from the toilet bowl.