EC Clinical and Medical Case Reports

Background and Objectives: Sodium and Potassium are the most investigated analytes in the routine clinical chemistry laboratories from different clinical departments. The measurement of serum electrolytes, i.e. sodium (Na⁺) and potassium (K⁺) of patients are crucial for clinical decision making. Nowadays, electrolyte analyzers use ion-selective electrode (ISE) based technologies which include: direct (dISE) and indirect (iISE). The iISE targets clinical laboratories while dISE serves at point-of-care settings. We mapped this study to evaluate the serum Na⁺ and serum K⁺ levels by both iISE and dISE methods and to correlate these values with serum total protein and serum albumin levels.

Methods: In this retrospective study, we analyzed the serum electrolytes and protein values of 348 patients. We juxtaposed the serum Na⁺ and serum K⁺ levels assessed through the direct (dISE) and indirect (iISE) methods. We also contrasted these values for the female and male participants with their serum total protein (TP) and serum albumin levels. The Shapiro-Wilk test was employed to determine the normality of the data distribution. We also correlated the obtained data for both direct (dISE) and indirect (iISE) methods. R software (version 4.4.1) was used for the data analysis.

Results: Out of 348 patients we analyzed, 110 (31.6%) were females. The median age of the study population was 54.0 (39.0-65.0) years. The median serum Na⁺ and serum K⁺ values of the study population were 139.0 (135.0-142.0) mEq/L and 4.4 (4.0-5.1) mEq/L, respectively. The median serum total protein and albumin levels of the study population were 6.8 (5.7-7.2) g/dL and 4.0 (2.9-4.3) g/dL, respectively. Our analysis revealed positive associations among the serum electrolytes and protein values.

Conclusion: We found that both direct (dISE) and indirect (iISE) methods can be used interchangeably for the estimation of serum Na⁺ and serum K⁺ levels. The correlation plots indicated that direct (dISE) method is more favorable than the indirect (iISE) method. However, the associations were not statistically significant.

 Keywords: Serum Electrolyte; Albumin; Total Protein; Beckman Coulter; Correlation

1. Flowers Kade C., et al. "Investigative algorithms for disorders affecting plasma sodium: a narrative review”. Journal of Laboratory and Precision Medicine26 (2022).
2. Cullin Alison and Andrew Trom. “Abnormal presentation of severe hyponatremia”. Cureus12 (2023): e50883.
3. Adrogué Horacio J., et al. “Diagnosis and management of hyponatremia: a review”. Journal of the American Medical Association3 (2022): 280-291.
4. Chopra Parul and Sudip Kumar Datta. “Discrepancies in electrolyte measurements by direct and indirect ion selective electrodes due to interferences by proteins and lipids”. Journal of Laboratory Physicians2 (2020): 84-91.
5. Malandrini Sabrina., et al. “Which laboratory technique is used for the blood sodium analysis in clinical research? A systematic review”. Clinical Chemistry and Laboratory Medicine9 (2021): 1501-1506.
6. Chacko Binila., et al. “Electrolytes assessed by point-of-care testing - Are the values comparable with results obtained from the central laboratory?” Indian Journal of Critical Care Medicine1 (2011): 24-29.
7. Stove Veronique., et al. “How to solve the underestimated problem of overestimated sodium results in the hypoproteinemic patient”. Critical Care Medicine2 (2016): e83-e88.
8. Dimeski Goce., et al. “Disagreement between ion selective electrode direct and indirect sodium measurements: estimation of the problem in a tertiary referral hospital”. Journal of Critical Care3 (2012): 326.e9-16.
9. Schindler Emily I. "Electrolytes and blood gases”. Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics-E-Book: Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics-E-Book (2014): 412.
10. Tel-Karthaus Nina., et al. “Instrument dependent erroneous sodium measurements in hypoproteinemic critically ill patients are causing significant misclassification of dysnatremias”. Clinical Chemistry and Laboratory Medicine9 (2019): e222-e225.v
11. Aziz Fahad., et al. “Pseudohyponatremia: Mechanism, diagnosis, clinical associations and management”. Journal of Clinical Medicine 12 (2023): 4076.
12. R Core Team. “R: A language and environment for statistical computing. R foundation for statistical computing” (2020).
13. Bajaj Jasmohan S., et al. “The impact of albumin use on resolution of hyponatremia in hospitalized patients with cirrhosis”. The American Journal of Gastroenterology9 (2018): 1339.
14. Tanemoto M. “Effect of serum albumin on serum sodium: necessity to consider the Donnan effect”. QJM: monthly journal of the Association of Physicians10 (2008): 827-828.
15. Nguyen Minhtri K., et al. “Defining the role of albumin infusion in cirrhosis-associated hyponatremia”. American Journal of Physiology. Gastrointestinal and Liver Physiology2 (2014): G229-G232.
16. Gómez-Hoyos Emilia., et al. “Hyponatremia in patients receiving parenteral nutrition: the importance of correcting serum sodium for total proteins. The role of the composition of parenteral nutrition in the development of hyponatremia”. European Journal of Clinical Nutrition3 (2018): 446-451.
17. Katrangi Waddah., et al. “Prevalence of clinically significant differences in sodium measurements due to abnormal protein concentrations using an indirect ion-selective electrode method”. The Journal of Applied Laboratory Medicine3 (2019): 427-432.