Ann Lab Med.  2015 Mar;35(2):238-241. 10.3343/alm.2015.35.2.238.

Evaluation of Random Urine Sodium and Potassium Compensated by Creatinine as Possible Alternative Markers for 24 Hours Urinary Sodium and Potassium Excretion

• Koo H
• Lee SG
• Kim JH

• KMID: 2363185
• DOI: http://doi.org/10.3343/alm.2015.35.2.238

Abstract

Sodium and potassium intake was assessed on the basis of its respective excretion levels in 24 hr urine samples. However, owing to the inconvenience of collection, we evaluated random spot urine for alternative sodium and potassium excretion markers. We included 250 patients who submitted 24 hr- and spot urine for clinical tests. However, 22 patients who showed 24 hr urine creatinine excretion levels <500 mg/day were excluded, because these samples possibly resulted from incomplete urine collection. Moreover, 24 patients were excluded because of their use of diuretics during the urine collection period. We observed significant correlations between 24 hr urine sodium excretion and both the sodium/creatinine (r=0.34, P<0.0001) and the sodium/specific gravity unit (SGU) ratios (r=0.19, P=0.007) in random urine samples. Similarly, 24 hr urine potassium excretion and both the spot urine potassium/creatinine (r=0.47, P<0.0001) and potassium/SGU ratios (r=0.28, P<0.0001) were significantly correlated. Although the estimated sodium/creatinine and potassium/creatinine ratios showed a significant correlation with 24 hr urine sodium and potassium excretion, respectively, further studies are required to develop a spot urine test for individualized monitoring of sodium and potassium excretion.

Keyword

24 hr urine; Sodium; Potassium; Excretion; Sodium/creatinine ratio; Potassium/creatinine ratio

MeSH Terms

Biomarkers/urine
Creatinine/*urine
Humans
Hypertension/pathology/urine
Potassium/*urine
Sodium/*urine
Urinalysis
Urine Specimen Collection
Biomarkers
Creatinine
Potassium
Sodium

Figure

• 

  Fig. 1 Correlations between 24 hr urine sodium or potassium excretion and random urine markers. Significant correlations exist between 24 hr urine sodium excretion and both the (A) Na+/Cr ratio (r=0.34, P<0.0001) and the (B) Na+/SGU ratio (r=0.19, P=0.007), as well as between 24-hr urine potassium excretion and both the (C) random urine K+/Cr ratio (r=0.47, P<0.0001) and the (D) random urine K+/SGU ratio (r=0.28, P<0.0001).Abbreviations: RU, random urine; Na+/Cr, sodium/creatinine ratio; K+/Cr, potassium/creatinine ratio; r, spearman's rank correlation coefficient; SGU, specific gravity unit, SGU is calculated as "(specific gravity-1)×100".

• 

  Fig. 2 Correlation between the Na+/K+ ratios of 24 hr and random urine. Significant correlations exist between 24 hr urine and random urine Na+/K+ (r=0.47, P<0.0001).

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