Comparison of Blood Gas Analysis and Auto-Analyzer Results for Sodium and Potassium Levels in Elderly and Non-elderly Adult Emergency Department Patients

TL;DR

This study compares blood gas and auto-analyzer results for sodium and potassium in elderly and non-elderly emergency department patients, finding greater variability in the elderly group.

Contribution

The study reveals that diagnostic precision for electrolyte levels may need adjustment for elderly patients due to greater measurement discrepancies.

Findings

Elderly patients showed a larger bias and wider limits of agreement for sodium measurements compared to non-elderly patients.

Potassium measurements in elderly patients also had greater discrepancies and lower concordance correlation coefficients.

The study highlights the need for tailored diagnostic approaches for elderly emergency department patients.

Abstract

Objectives

This study aims to evaluate the concordance between blood gas and biochemical measurement methods for sodium and potassium levels in elderly and non-elderly patients within an emergency department (ED) setting.

Methods

A retrospective method comparison study was conducted at an ED from February 1, 2023, to March 1, 2023. The study included 414 patients, categorized into "elderly" (aged 65 and above; n = 138, 33.3%) and "non-elderly" (aged 18 to 64; n = 276, 66.7%) groups. Concordance was assessed using Bland-Altman, Passing-Bablok, and Lin's concordance correlation methods.

Results

In sodium measurements, the elderly group exhibited an average bias of −1.52 mEq/L (95% confidence interval [CI] −2.12 to −0.92), with lower and upper limits of agreement (LoA) at −8.46 and 5.42 mEq/L, respectively, indicating a broader variance than non-elderly patients, who showed an average bias of −0.82 mEq/L with limits of −4.97 to 3.32 mEq/L. For potassium, the elderly group's average bias was −0.46 mEq/L (95% CI −0.36 to −0.57), with limits of agreement from −1.68 to 0.75 mEq/L, compared to non-elderly patients with a bias of −0.29 mEq/L and limits of −0.71 to 0.13 mEq/L. Furthermore, concordance correlation coefficients revealed a reduced agreement in the elderly for both sodium (rccc = 0.799) and potassium (rccc = 0.529) compared to the non-elderly cohort (sodium rccc = 0.821, potassium rccc = 0.715).

Conclusion

The study identifies significant discrepancies in sodium and potassium levels between elderly and non-elderly patients, suggesting a need for diagnostic precision. It emphasizes the importance of customizing diagnostic approaches to better serve the elderly population in EDs.

Figures