title: A simple method for estimating 24 h urinary sodium and potassium excretion from second morning voiding urine specimen in adults.
abstract: 1. An assessment was made of the extent sodium (Na) and potassium (K) intake can be estimated from Na, K and creatinine (Cr) content of a second morning voiding urine (SMU) specimen collected within 4 h after the first voiding upon awakening but before breakfast in 159 clinically healthy, free-living individuals (20-79 years). The SMU and the rest of 24 h urine specimens for a 3-5 day period were collected. 2. The following equations for estimating 24 h urinary Na (24HUNaV) and K (24HUKV) excretions were developed, and the accuracy and the reliability of these equations were evaluated. Estimated value of 24HUNaV (mEq/day) = 16.3 square root of XNa; estimated value of 24HUKV (mEq/day) = 7.2 square root of XK, where XNa (or XK) = SMUNa (or SMUK)/SMUCr x predicted 24 h urinary Cr excretion. 3. Highly statistically significant correlations were detected between the values estimated and measured for both Na (r = 0.728, P < 0.001, n = 159) and K (r = 0.780, P < 0.001, n = 159). 4. These equations were applied to Group 1 subjects, who collected the urine for a single day, and to Group 2, for 3 days. The correlation coefficients between the values estimated and measured for Na and K were 0.531 and 0.443 in Group 1, and 0.821 and 0.590 in Group 2, respectively. No statistically significant differences were observed. 5. The SMU specimens provide a satisfactory alternative to both 24HUNaV and 24HUKV in adults for extensive epidemiological surveys but also for clinical application.
authors.affiliation: Institute of Health Science, Kyushu University, Kasuga, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kawasaki
authors.forename: K
authors.initials: K
authors.lastname: Itoh
authors.forename: K
authors.initials: K
authors.lastname: Uezono
authors.forename: H
authors.initials: H
authors.lastname: Sasaki
mesh_terms: D000328:Adult; D000368:Aged; D002940:Circadian Rhythm; D003404:Creatinine / Q000652:urine; D005260:Female; D006801:Humans; D008297:Male; D008432:Mathematical Computing; D008875:Middle Aged; D011188:Potassium / Q000652:urine*; D011237:Predictive Value of Tests; D012737:Sex Factors; D012964:Sodium / Q000652:urine*
chemical_list: D012964:Sodium; D003404:Creatinine; D011188:Potassium