Spot Urine Samples to Estimate Na and K Intake in Patients With Chronic Kidney Disease and Healthy Adults: A Secondary Analysis From a Controlled Feeding Study

Andrea J. Lobene, Elizabeth R. Stremke, George P. McCabe, Sharon M. Moe, Ranjani N. Moorthi, Kathleen M. Hill Gallant

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6 Scopus citations

Abstract

OBJECTIVE: The objective of this study was to assess the agreement between estimated 24-hour urinary sodium excretion (e24hUNa) and estimated 24-hour urinary potassium excretion (e24hUK), calculated from a spot urine sample using several available equations and actual sodium and potassium intake from a controlled diet in both healthy participants and those with chronic kidney disease (CKD).

DESIGN AND METHODS: This study is a secondary analysis of a controlled feeding study in CKD patients matched to healthy controls. Participants (n = 16) consumed the controlled diet, which provided ∼2400 mg Na/day and ∼3000 mg K/day, for 8 days. On days 7 and 8, participants consumed all meals and collected all urine in an inpatient research setting, and they were discharged on day 9. The day 7 morning spot urine sample was used to calculate e24hUNa and e24hUK, which was compared with known sodium and potassium intake, respectively.

RESULTS: Average e24hUNa from the INTERSALT and Tanaka-Na equations were higher than actual sodium intake by 373 mg and 559 mg, respectively, though the differences were not significant. e24hUNa from the Nerbass-SALTED equation in CKD participants was significantly higher than actual sodium intake by ∼2000 mg (P < .001), though e24hUNa from the Nerbass-RRID equation was not different from intake. e24hUK from the Tanaka-K equation was significantly lower than actual potassium intake (P < .001). For both e24hUNa and e24hUK for all participants, agreement with actual intake was poor, and e24hUNa and e24hUK were not correlated with actual sodium or potassium intake, respectively.

CONCLUSION: e24hUNa and e24hUK are poor indicators of true sodium and potassium intake, respectively, in both healthy and CKD participants. Findings should be confirmed in larger sample sizes with varying levels of dietary sodium and potassium.

Original languageEnglish (US)
Pages (from-to)602-610
Number of pages9
JournalJournal of Renal Nutrition
Volume31
Issue number6
DOIs
StatePublished - Nov 2021

Bibliographical note

Funding Information:
Support: This work was supported by the National Institutes of Health (KHG: K01DK102864 and RM: K23DK102824 ), (SMM: P30 AR072581-01 and R01DK110871 ) and the Indiana Clinical and Translational Sciences Institute (AJL and ERS), which is supported by 2 awards from the National Institutes of Health (Grant # UL1TR002529 and Grant # TL1TR002531 ). The funders had no role in the study design, the collection/interpretation of data, or the writing and publication of findings.

Funding Information:
The authors are grateful for the support provided by the Clinical Research Center at Purdue University and at the Indiana University School of Medicine. The authors report no conflicts of interest. Financial Disclosure: The authors declare that they have no relevant financial interests. Support: This work was supported by the National Institutes of Health (KHG: K01DK102864 and RM: K23DK102824), (SMM: P30 AR072581-01 and R01DK110871) and the Indiana Clinical and Translational Sciences Institute (AJL and ERS), which is supported by 2 awards from the National Institutes of Health (Grant # UL1TR002529 and Grant # TL1TR002531). The funders had no role in the study design, the collection/interpretation of data, or the writing and publication of findings.

Publisher Copyright:
© 2020 National Kidney Foundation, Inc.

PubMed: MeSH publication types

  • Journal Article

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