Reliability of Arterial Blood Gas Analyzer for Electrolyte and Hemoglobin Measurement: A Method Comparison Study

Rapid assessment of electrolytes and hemoglobin is crucial in emergency and critical care. Arterial blood gas (ABG) analyzers are widely used as point-of-care devices. However, their agreement with central laboratory measurements remains uncertain because of methodological differences. This study aimed to evaluate the reliability of sodium, potassium, chloride, and hemoglobin values obtained from an ABG analyzer compared with those from a central laboratory autoanalyzer and to assess analytical acceptability using US Clinical Laboratory Improvement Amendments (CLIA) 2025 allowable error limits.

In this prospective observational study, 200 paired arterial and venous samples from patients in the Emergency Department were analyzed. Arterial samples were processed on an ABG analyzer using direct ion-selective electrode (ISE) methodology, and venous serum electrolytes were measured on a central laboratory autoanalyzer using indirect ISE methodology. Hemoglobin was measured on a hematology analyzer. Paired comparisons were performed using the Wilcoxon signed-rank test, correlation was assessed with Spearman's coefficient, agreement was assessed with Bland-Altman analysis, and total error was compared with CLIA limits.

ABG-derived sodium and potassium values were significantly lower than venous laboratory values, whereas chloride and hemoglobin values were significantly higher (p < 0.001). All analytes showed strong positive correlations. Bland-Altman analysis demonstrated acceptable agreement for sodium (bias, -2.8 mmol/L) and potassium (bias, -0.2 mmol/L), both within CLIA allowable limits. Chloride showed a total error of 6.43%, and hemoglobin showed a total error of 15.15%, indicating unacceptable analytical error.

ABG-derived sodium and potassium values demonstrated acceptable agreement with central laboratory measurements and can be used for rapid clinical decision-making in emergency settings. However, chloride and hemoglobin values should not be used interchangeably without institution-specific validation and correction equations.