Clinical and Experimental Nephrology

, Volume 15, Issue 6, pp 861–867

Validation of the equations for estimating daily sodium excretion from spot urine in patients with chronic kidney disease

Authors

    • Department of NephrologyNagoya University Graduate School of Medicine
  • Yoshinari Yasuda
    • Department of CKD InitiativesNagoya University Graduate School of Medicine
  • Masaru Horio
    • Department of Functional Diagnostic ScienceOsaka University Graduate School of Medicine
  • Kanako Shibata
    • Department of CKD InitiativesNagoya University Graduate School of Medicine
  • Sawako Kato
    • Department of CKD InitiativesNagoya University Graduate School of Medicine
  • Yu Mizutani
    • Department of CKD InitiativesNagoya University Graduate School of Medicine
  • Junko Imai
    • Department of CKD InitiativesNagoya University Graduate School of Medicine
  • Mutsuharu Hayashi
    • Department of CKD InitiativesNagoya University Graduate School of Medicine
  • Hideki Kamiya
    • Department of CKD InitiativesNagoya University Graduate School of Medicine
  • Yutaka Oiso
    • Department of Endocrinology and DiabetologyNagoya University Graduate School of Medicine
  • Toyoaki Murohara
    • Departmant of Cardiovascular MedicineNagoya University Graduate School of Medicine
  • Shoichi Maruyama
    • Department of NephrologyNagoya University Graduate School of Medicine
  • Seiichi Matsuo
    • Department of NephrologyNagoya University Graduate School of Medicine
Original Article

DOI: 10.1007/s10157-011-0523-0

Cite this article as:
Imai, E., Yasuda, Y., Horio, M. et al. Clin Exp Nephrol (2011) 15: 861. doi:10.1007/s10157-011-0523-0

Abstract

Background

Measuring sodium excretion in a 24-h urine collection is the most reliable method of estimating salt intake, but it is not applicable to all patients. As an alternative, equations for estimating Na excretion from Japanese by a spot urine sample were created, but they have not been validated in patients with chronic kidney disease (CKD), which are frequently associated with nocturia and medication.

Methods

We enrolled 136 patients with CKD and collected both 24-h urine and the first morning urine. Na excretion was estimated from the first morning urine by Kawasaki’s equation, which was originally used for the second morning urine, and Tanaka’s equation, which is applied for spot urine samples taken at any time from 9 am to 7 pm. We evaluated the two equations for bias, RMSE and accuracy within 30 and 50% of the measured Na excretion.

Results

Bias, RMSE and accuracy within 30% of the estimated Na excretion were 48 ± 69 and 2 ± 69 mmol/day, 84 and 69 mmol/day, and 35 and 49% using Kawasaki’s equation and Tanaka’s equation, respectively. Na excretion in the first morning urine was accurately estimated by Tanaka’s equation, but it was overestimated by Kawasaki’s equation. Nocturia and medication such as diuretics and ACE inhibitor or angiotensin receptor blocker did not affect the accuracy with which Na excretion was estimated by Tanaka’s equation substantially.

Conclusion

Tanaka’s equation for estimating Na excretion from the first morning urine in patients with CKD is accurate enough for use in clinical practice.

Keywords

SodiumCreatinineCKDEstimated Na excretion

Copyright information

© Japanese Society of Nephrology 2011