Estimation of daily sodium and potassium excretion from overnight urine of Japanese children and adolescents.

ABSTRACT:

Background

Estimates of daily sodium (Na) and potassium (K) excretion were explicitly biased when using equations for adults. We aimed to develop equations to estimate them using overnight urine from Japanese children and adolescents.

Methods

The subjects comprised 70 students aged 10.49-15.76?years: validation group, n = 34; and verification group, n = 36. Each subject performed two operations of overnight spot urine (U_m) and 24-h urine (U₂₄) sampling. Concentrations of Na, K, and creatinine (Cr) were measured, and anthropometrics were recorded. In the validation group, Na/Cr, and K/Cr (mEq L^-1/mg dL^-1) in 24-h urine were predicted from their correspondents in overnight urine. Daily Cr excretion (EstCr₂₄; mg d^-1) was estimated according to Mage's method.

Results

In validation, we formulated Na excretion (mg d^-1) = 23 × exp (0.2085) × [(Na/CrU_m + 1)^1.0148 - 1] × 1.078 × EstCr₂₄/10; and K excretion (mg d^-1) = 39 × exp (0.0315) × [(K/CrU_m + 1)^1.3165 - 1] × 1.078 × EstCr₂₄/10. For verification, we compared estimates with the measured 24-h Na excretion 3596 ± 1058?mg d^-1, and K excretion 1743 ± 569?mg d^-1. The mean biases and intraclass correlations (3, 1) were -131?mg d^-1 and 0.60, respectively for Na excretion; and -152?mg d^-1 and 0.55 for K excretion.

Conclusion

We obtained validated equations to estimate daily Na and K excretion with accessible variables such as Na, K, and Cr concentrations of overnight urine, body height and weight, and age for children and adolescents. When using the obtained equations, caution should be paid to small but definite biases and measurement errors.

SUBMITTER: Okuda M 

PROVIDER: S-EPMC7697364 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature