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Prevalence of pseudonatremia in a clinical laboratory – role of the water content

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Published/Copyright: September 27, 2016
Clinical Chemistry and Laboratory Medicine (CCLM)
From the journal Clinical Chemistry and Laboratory Medicine (CCLM) Volume 55 Issue 4

Abstract

Background:

Sodium concentration is a frequently used marker to discriminate between differential diagnoses or for clinical follow-up. Pseudonatremia, as a result of indirect ion-selective electrode (ISE) measurements in automated chemistry analyzers, can lead to incorrect diagnosis and treatment. We investigated whether the estimated water content, based on total protein and lipid concentrations, can be used to reduce diagnoses of pseudonatremia.

Methods:

Indirect and direct ISE measurements of sodium were compared in blood samples from intensive care unit (ICU) (n = 98) and random non-ICU patients (n = 100). Differences between direct measurements using whole blood and lithium-heparin plasma were also determined. Water content, estimated by a linear combination of total protein and lipid concentrations, was used to correct indirectly measured sodium concentrations. The prevalence of pseudonatremia was evaluated in the ICU patient group.

Results:

An absolute difference of 3 mmol/L was observed between direct measurements using lithium-heparin plasma and whole blood, with higher concentrations in plasma. Additionally, we observed that differences between indirect and direct measurements displayed a linear relationship with the estimated water content. The prevalence of pseudohypernatremia after indirect measurements (32%) was reduced when measurements were corrected for water content (19%).

Conclusions:

In critically ill patients, sodium concentrations should be preferably measured by direct measurements. Whole blood is the preferred material for these measurements. For routine sodium analyses in other patients, correction using the estimated water content appears promising in reducing the prevalence of pseudohypernatremia by indirect measurements.

Keywords: ion-selective electrode; method comparison; pseudonatremia; water content

Acknowledgments

The authors would to thank Stan van Dijk, Inge Bakker, and John Benco (Siemens diagnostics) as well as Maarten Nijsten and Annemieke Oude Lansink-Hartgring (University Medical Centre Groningen) for helpful suggestions and discussions.

  1. Author contributions:All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: None declared.

  3. Employment or leadership:None declared.

  4. Honorarium: None declared.

  5. Competing interests:The funding organization(s) played no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication.

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Supplemental Material:

The online version of this article (DOI: 10.1515/cclm-2016-0401) offers supplementary material, available to authorized users.

Received: 2016-5-6
Accepted: 2016-8-19
Published Online: 2016-9-27
Published in Print: 2017-3-1

©2017 Walter de Gruyter GmbH, Berlin/Boston

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https://doi.org/10.1515/cclm-2016-0401
Keywords for this article
ion-selective electrode; method comparison; pseudonatremia; water content

Articles in the same Issue

  1. Frontmatter
  2. Editorial
  3. The central role of external quality assurance in harmonisation and standardisation for laboratory medicine
  4. Review
  5. Fecal calprotectin in inflammatory bowel diseases: update and perspectives
  6. Mini Review
  7. Factor VIIa-antithrombin complex: a possible new biomarker for activated coagulation
  8. Opinion Papers
  9. Improving quality in the preanalytical phase through innovation, on behalf of the European Federation for Clinical Chemistry and Laboratory Medicine (EFLM) Working Group for Preanalytical Phase (WG-PRE)
  10. Metabolite profiling can change health-care delivery to obese patients with fatty liver disease: the search for biomarkers
  11. Genetics and Molecular Diagnostics
  12. Rapid screening for targeted genetic variants via high-resolution melting curve analysis
  13. Evaluation of the new cobas® HCV genotyping test based on real-time PCRs of three different HCV genome regions
  14. General Clinical Chemistry and Laboratory Medicine
  15. Harmonisation of serum dihydrotestosterone analysis: establishment of an external quality assurance program
  16. Spanish Preanalytical Quality Monitoring Program (SEQC), an overview of 12 years’ experience
  17. Peer groups splitting in Croatian EQA scheme: a trade-off between homogeneity and sample size number
  18. Prevalence of pseudonatremia in a clinical laboratory – role of the water content
  19. Retrospective validation of a β-trace protein interpretation algorithm for the diagnosis of cerebrospinal fluid leakage
  20. Economic evaluation of procalcitonin-guided antibiotic therapy in acute respiratory infections: a Chinese hospital system perspective
  21. Performance evaluation of ImmunoCAP® ISAC 112: a multi-site study
  22. Clinical autoantibody detection by microarray
  23. Cardiovascular Diseases
  24. Kinetics of troponin I in patients with myocardial injury after noncardiac surgery
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