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

Clinical and Experimental Nephrology volume 15, pages 861–867 (2011)Cite this article

An Erratum to this article was published on 23 March 2013

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.

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Acknowledgments

This study was supported by a grant from the Ministry of Health, Labor and Welfare.

Author information

Affiliations

  1. Department of Nephrology, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya, 466-8550, Japan

    Enyu Imai, Shoichi Maruyama & Seiichi Matsuo

  2. Department of CKD Initiatives, Nagoya University Graduate School of Medicine, Nagoya, Japan

    Yoshinari Yasuda, Kanako Shibata, Sawako Kato, Yu Mizutani, Junko Imai, Mutsuharu Hayashi & Hideki Kamiya

  3. Department of Functional Diagnostic Science, Osaka University Graduate School of Medicine, Suita, Japan

    Masaru Horio

  4. Departmant of Cardiovascular Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan

    Toyoaki Murohara

  5. Department of Endocrinology and Diabetology, Nagoya University Graduate School of Medicine, Nagoya, Japan

    Yutaka Oiso

Authors
  1. Enyu Imai
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  2. Yoshinari Yasuda
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  3. Masaru Horio
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  4. Kanako Shibata
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  5. Sawako Kato
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  6. Yu Mizutani
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  7. Junko Imai
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  8. Mutsuharu Hayashi
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  9. Hideki Kamiya
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  10. Yutaka Oiso
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  11. Toyoaki Murohara
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  12. Shoichi Maruyama
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  13. Seiichi Matsuo
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Corresponding author

Correspondence to Enyu Imai.

Additional information

A part of this study was presented at ERA-EDTA 2011 at Plague.

An erratum to this article can be found online at http://dx.doi.org/10.1007/s10157-013-0791-y.

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Imai, E., Yasuda, Y., Horio, M. et al. Validation of the equations for estimating daily sodium excretion from spot urine in patients with chronic kidney disease. Clin Exp Nephrol 15, 861–867 (2011). https://doi.org/10.1007/s10157-011-0523-0

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  • DOI: https://doi.org/10.1007/s10157-011-0523-0

Keywords

  • Sodium
  • Creatinine
  • CKD
  • Estimated Na excretion