Twenty-Four-Hour Urine Osmolality as a Physiological Index of Adequate Water Intake

Table 1

Bivariate relationships between total fluid intake (TFI), 24 h urine volume (U_vol), and osmolality (24 h U_Osm).

Reference	Description	Criterion value	UOsm cutoff value derived from ROC analyses	Sensitivity	Specificity
EFSA [1]	Dietary reference value for total fluid intake (estimated to be 80% of total water intake)	TFI ≥ 2.0 L·d^−1 (men) or; ≥ 1.6 L·d^−1 (women)	544 mOsm·kg^−1	0.86	0.80
Curhan et al. [4]	Multivariate-adjusted odds-ratio (OR) for kidney stones in women with higher TFI	TFI ≥ 1850 mL·d^−1	525 mOsm·kg^−1	0.95	0.77
Borghi et al. [23]	In recurrent stone formers, increasing 24 h UVol resulted in a 50% lower stone recurrence rate over 5 years	24 h UVol ≥ 2.0 L·d^−1	448 mOsm·kg^−1	0.98	0.82