Clinical and Experimental Nephrology

, Volume 15, Issue 6, pp 861–867 | Cite as

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

  • Enyu Imai
  • Yoshinari Yasuda
  • Masaru Horio
  • Kanako Shibata
  • Sawako Kato
  • Yu Mizutani
  • Junko Imai
  • Mutsuharu Hayashi
  • Hideki Kamiya
  • Yutaka Oiso
  • Toyoaki Murohara
  • Shoichi Maruyama
  • Seiichi Matsuo
Original Article

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

Sodium Creatinine CKD Estimated Na excretion 

Notes

Acknowledgments

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

References

  1. 1.
    Strazzullo P, D’Elia L, Kandala NB, Cappuccio FP. Salt intake, stroke, and cardiovascular disease: meta-analysis of prospective studies. BMJ. 2009;339:b4567.PubMedCrossRefGoogle Scholar
  2. 2.
    Cook NR, Cutler JA, Obarzanek E, Buring JE, Rexrode KM, Kumanyika SK, Appel LJ, Whelton PK. Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP). BMJ. 2007;334(7599):885–8.PubMedCrossRefGoogle Scholar
  3. 3.
    Intersalt Cooperative Research Group. Intersalt: an international study of electrolyte excretion and blood pressure. Results for 24 hour urinary sodium and potassium excretion. BMJ. 1988;297(6644):319–28.Google Scholar
  4. 4.
    Hooper L, Bartlett C, Davey Smith G, Ebrahim S. Reduced dietary salt for prevention of cardiovascular disease. Cochrane Database Syst Rev. 2003;3:CD003656.Google Scholar
  5. 5.
    Bibbins-Domingo K, Chertow GM, Coxson PG, Moran A, Lightwood JM, Pletcher MJ, Goldman L. Projected effect of dietary salt reductions on future cardiovascular disease. N Engl J Med. 2010;362(7):590–9.PubMedCrossRefGoogle Scholar
  6. 6.
    The Japanese Society of Hypertension. Guidelines (JSH 2009). Chapter 4: lifestyle modifications. Hypertens Res. 2009;32:29–32.Google Scholar
  7. 7.
    Kawano Y, Tsuchihashi T, Matsuura H, Ando K, Fujita T, Ueshima H. Report of the Working Group for Dietary Salt Reduction of the Japanese Society of Hypertension. 2. Assessment of salt intake in the management of hypertension. Hypertens Res. 2007;30(10):887–93.Google Scholar
  8. 8.
    Kamata K, Tochikubo O. Estimation of 24-h urinary sodium excretion using lean body mass and overnight urine collected by a pipe-sampling method. J Hypertens. 2002;20(11):2191–7.PubMedCrossRefGoogle Scholar
  9. 9.
    Kawasaki T, Itoh K, Uezono K, Sasaki H. A simple method for estimating 24 h urinary sodium and potassium excretion from second morning voiding urine specimen in adults. Clin Exp Pharmacol Physiol. 1993;20(1):7–14.PubMedCrossRefGoogle Scholar
  10. 10.
    Kawasaki T, Itoh K, Uezono K, Ogaki T, Yoshimizu Y, Kobayashi S, Osaka T, Ogata M, Dhungel S, Sharma S, et al. Investigation of high salt intake in a Nepalese population with low blood pressure. J Hum Hypertens. 1993;7(2):131–40.PubMedGoogle Scholar
  11. 11.
    Hashimoto T, Yagami F, Owada M, Sugawara T, Kawamura M. Salt preference according to a questionnaire vs. dietary salt intake estimated by a spot urine method in participants at a health check-up center. Intern Med. 2008;47(5):399–403.PubMedCrossRefGoogle Scholar
  12. 12.
    Iseki K, Iseki C, Itoh K, Uezono K, Sanefuji M, Ikemiya Y, Fukiyama K, Kawasaki T. Urinary excretion of sodium and potassium in a screened cohort in Okinawa, Japan. Hypertens Res. 2002;25(5):731–6.PubMedCrossRefGoogle Scholar
  13. 13.
    Kawamura M, Kusano Y, Takahashi T, Owada M, Sugawara T. Effectiveness of a spot urine method in evaluating daily salt intake in hypertensive patients taking oral antihypertensive drugs. Hypertens Res. 2006;29(6):397–402.PubMedCrossRefGoogle Scholar
  14. 14.
    Tanaka T, Okamura T, Miura K, Kadowaki T, Ueshima H, Nakagawa H, Hashimoto T. A simple method to estimate populational 24-h urinary sodium and potassium excretion using a casual urine specimen. J Hum Hypertens. 2002;16(2):97–103.PubMedCrossRefGoogle Scholar
  15. 15.
    Tamaki J, Kikuchi Y, Yoshita K, Takebayashi T, Chiba N, Tanaka T, Okamura T, Kasagi F, Minai J, Ueshima H. Stages of change for salt intake and urinary salt excretion: baseline results from the High-Risk and Population Strategy for Occupational Health Promotion (HIPOP-OHP) study. Hypertens Res. 2004;27(3):157–66.PubMedCrossRefGoogle Scholar
  16. 16.
    Fukuda M, Motokawa M, Miyagi S, Sengo K, Muramatsu W, Kato N, Usami T, Yoshida A, Kimura G. Polynocturia in chronic kidney disease is related to natriuresis rather than to water diuresis. Nephrol Dial Transplant. 2006;21:2172–7.PubMedCrossRefGoogle Scholar
  17. 17.
    Uzu T, Kimura G. Diuretics shift circadian rhythm of blood pressure from nondipper to dipper in essential hypertension. Circulation. 1999;100(15):1635–8.PubMedCrossRefGoogle Scholar
  18. 18.
    Fukuda M, Yamanaka T, Mizuno M, Motokawa M, Shirasawa Y, Miyagi S, Nishio T, Yoshida A, Kimura G. Angiotensin II type 1 receptor blocker, olmesartan, restores nocturnal blood pressure decline by enhancing daytime natriuresis. J Hypertens. 2008;26(3):583–8.PubMedCrossRefGoogle Scholar
  19. 19.
    Kawamura M, Hashimoto T, Owada M, Sugawara T. The influence of posture on the estimation of daily salt intake by the second morning urine method. Hypertens Res. 2010;33:505–10.PubMedCrossRefGoogle Scholar
  20. 20.
    Ogihara T, Kikuchi K, Matsuoka H, Fujita T, Higaki J, Horiuchi M, Imai Y, Imaizumi T, Ito S, Iwao H, Kario K, Kawano Y, Kim-Mitsuyama S, Kimura G, Matsubara H, Matsuura H, Naruse M, Saito I, Shimada K, Shimamoto K, Suzuki H, Takishita S, Tanahashi N, Tsuchihashi T, Uchiyama M, Ueda S, Ueshima H, Umemura S, Ishimitsu T, Rakugi H. The Japanese Society of Hypertension guidelines for the management of hypertension (JSH 2009). Hypertens Res. 2009;32(1):3–107.PubMedCrossRefGoogle Scholar
  21. 21.
    Japanese Society of Nephrology. Evidence-based practice guideline for the treatment of CKD. Clin Exp Nephrol. 2009;13(6):537–66.Google Scholar

Copyright information

© Japanese Society of Nephrology 2011

Authors and Affiliations

  • Enyu Imai
    • 1
  • Yoshinari Yasuda
    • 2
  • Masaru Horio
    • 3
  • Kanako Shibata
    • 2
  • Sawako Kato
    • 2
  • Yu Mizutani
    • 2
  • Junko Imai
    • 2
  • Mutsuharu Hayashi
    • 2
  • Hideki Kamiya
    • 2
  • Yutaka Oiso
    • 5
  • Toyoaki Murohara
    • 4
  • Shoichi Maruyama
    • 1
  • Seiichi Matsuo
    • 1
  1. 1.Department of NephrologyNagoya University Graduate School of MedicineNagoyaJapan
  2. 2.Department of CKD InitiativesNagoya University Graduate School of MedicineNagoyaJapan
  3. 3.Department of Functional Diagnostic ScienceOsaka University Graduate School of MedicineSuitaJapan
  4. 4.Departmant of Cardiovascular MedicineNagoya University Graduate School of MedicineNagoyaJapan
  5. 5.Department of Endocrinology and DiabetologyNagoya University Graduate School of MedicineNagoyaJapan

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