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https://doi.org/10.11613/BM.2019.011002

Case report: An index of suspicion in hyponatraemia

Marizna Barkhuizen ; Division of Chemical Pathology, National Health Laboratory Service (NHLS) and University of Stellenbosch, Tygerberg Hospital, Cape Town, South Africa
Mariza Hoffmann ; Division of Chemical Pathology, National Health Laboratory Service (NHLS) and University of Stellenbosch, Tygerberg Hospital, Cape Town, South Africa
Ekkehard WA Zöllner ; Department of Paediatrics, Faculty of Medicine and Health Sciences, University of Stellenbosch, Cape Town, South Africa
Rajiv T. Erasmus ; Division of Chemical Pathology, National Health Laboratory Service (NHLS) and University of Stellenbosch, Tygerberg Hospital, Cape Town, South Africa
Annalise E. Zemlin orcid.org/0000-0001-7621-4679 ; Division of Chemical Pathology, National Health Laboratory Service (NHLS) and University of Stellenbosch, Tygerberg Hospital, Cape Town, South Africa

Abstract

Serum indices can give valuable information and should be interpreted as a result. Lipaemia can influence results through different mechanisms, an
important one being the electrolyte exclusion effect. A case of pseudohyponatraemia due to this is reported. A 15-year-old female with type 2 diabetes
was seen for follow-up. Her biochemistry results revealed severe hyponatraemia of 118 mmol/L. Her capillary glucose concentration was 13.7
mmol/L with a corrected sodium of 122 mmol/L. A lipaemic index of 3+ (absolute value 1320) was noted, which was not flagged by the laboratory
information system, as it was below the critical lipaemia limit for sodium determination. Repeated analysis of the same sample using a direct ion
selective electrode method, the serum sodium concentration was 134 mmol/L (sodium corrected for glucose = 138 mmol/L). A triglyceride concentration
was requested, which was severely raised (100.1 mmol/L). The electrolyte exclusion effect is an analytical phenomenon that causes falsely
low electrolyte concentrations in the presence of severe lipaemia or hyperproteinaemia when using indirect analytical methods. These methods are
used on many modern-day automated chemistry analysers and should be considered in a patient with asymptomatic hyponatraemia.

Keywords

pseudohyponatraemia; electrolyte exclusion effect; case report; serum indices; endogenous interference

Hrčak ID:

213862

URI

https://hrcak.srce.hr/213862

Publication date:

15.2.2019.

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