Pakistan Journal of Medical Research (May 2024)
A Comparative Analysis of Serum Sodium Level Utilizing Direct and Indirect Ion Selective Electrode in Critically Ill Patients with Hypoalbuminemia: Methodological Insights and Clinical Implications
Abstract
Background: Serum electrolytes are one of the most frequently requested tests in patients from critical care settings. Methodsfor estimation of serum electrolytes include direct and indirect ion selective electrode (ISE). In case of indirect ISE, the pre-analytical dilution step can result in pseudonormonatremia or pseudohypernatremia in setting of hypoalbuminemia. Discrepancy in sodium results can lead to the misdiagnosis and mismanagement of critically ill patients. Objective: To evaluate the difference of mean serum sodium level measured by direct and indirect ISE in critically ill patients with hypoalbuminemia. Study type,settings & duration: This cross-sectional study conducted in Department of Chemical Pathology, Sheikh Zayed Hospital,Rahim Yar Khan from February to August 2022. Methodology: A total 408 study subjects aged between 20 to 60 years admitted in intensive care units of Sheikh Zayed hospital Rahim yar khan with serum albumin level <3.5g/dl were included in study. Serum sodium level was estimated concurrently by both methods for all study subjects satisfying the inclusion criteria. Mean difference of serum sodium level measured by both methods was evaluated to see the statistically significant difference between two methods. Results: Mean difference of serum sodium level measured by indirect and direct ISE (Indirect ISE-direct ISE) was 4.216±13.571mmol/L withstatistically significant difference (pvalue: 0.000). The difference was not acceptable according to CLIA (Clinical Laboratory Improvement Amendments) requirements for acceptable performance between the methods. Effect of triglyceride was statistically significant for mean difference of serum sodium level between two methods (pvalue: 0.026). No statistically significant difference of mean difference of serum sodium level with respect to other variables was found. Conclusion: Interchangeable use of directand indirect ISE should be avoided in the setting of hypoalbuminemia. Indirect ion selective electrode results of serum sodium level are misleading in the setting of hypoalbuminemia and critically ill patients can be misdiagnosed and mismanaged if sodium level is measured by indirect ion selective electrode. Standardization should be considered by hospital laboratories to use direct ISE for serum sodium measurement.
