Urine Reagent Strips Are Inaccurate for Assessing Hypohydration: A Brief Report.

OBJECTIVE: To assess the diagnostic ability of urine reagent strips to identify hypohydration based on urine specific gravity (USG).

DESIGN: This study examined the agreement of USG between strips and refractometry with Bland-Altman, whereas the diagnostic ability of the strips to assess hypohydration was performed by receiver operating characteristic analysis.

SETTING: Arkansas high school football preseason practice.

PARTICIPANTS: Four hundred fourteen fresh urine samples were analyzed.

MAIN OUTCOME MEASURES: Urine specific gravity was assessed by both reagent strips and refractometry. Cutoffs of >1.020 and >1.025 were used for identifying hypohydration.

RESULTS: Bland-Altman analysis showed agreement of the 2 methods. Overall diagnostic ability of the urine strip to identify hypohydration was fair (area under the curve 72%-78%). However, the sensitivity to correctly identify hypohydration was poor (63%-71%), and the specificity of correctly identifying euhydration was poor to fair (68%-83%).

CONCLUSION: The urine strip method is not valid for assessing hypohydration.