title: Validation of the equations for estimating daily sodium excretion from spot urine in patients with chronic kidney disease.
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.
  
  
  CONCLUSIONS
  Tanaka's equation for estimating Na excretion from the first morning urine in patients with CKD is accurate enough for use in clinical practice.
authors: Department of Nephrology, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-8550, Japan. imai@med.nagoya-u.ac.jp
authors: Enyu
authors: E
authors: Imai
authors: Yoshinari
authors: Y
authors: Yasuda
authors: Masaru
authors: M
authors: Horio
authors: Kanako
authors: K
authors: Shibata
authors: Sawako
authors: S
authors: Kato
authors: Yu
authors: Y
authors: Mizutani
authors: Junko
authors: J
authors: Imai
authors: Mutsuharu
authors: M
authors: Hayashi
authors: Hideki
authors: H
authors: Kamiya
authors: Yutaka
authors: Y
authors: Oiso
authors: Toyoaki
authors: T
authors: Murohara
authors: Shoichi
authors: S
authors: Maruyama
authors: Seiichi
authors: S
authors: Matsuo
mesh_terms: D000368:Aged; D047228:Angiotensin II Type 1 Receptor Blockers / Q000627:therapeutic use; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000627:therapeutic use; D015415:Biomarkers / Q000652:urine; D003404:Creatinine / Q000652:urine; D004232:Diuretics / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007564:Japan; D007674:Kidney Diseases / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology / Q000652:urine; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009318:Natriuresis / Q000187:drug effects; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012964:Sodium / Q000652:urine*; D017673:Sodium Chloride, Dietary / Q000652:urine; D016482:Urinalysis
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D000806:Angiotensin-Converting Enzyme Inhibitors; D015415:Biomarkers; D004232:Diuretics; D017673:Sodium Chloride, Dietary; D012964:Sodium; D003404:Creatinine