Analysis of Bias in Measurements of Potassium, Sodium and Hemoglobin by an Emergency Department-Based Blood Gas Analyzer Relative to Hospital Laboratory Autoanalyzer Results

Abstract

ObjectiveThe emergency departments (EDs) of Chinese hospitals are gradually being equipped with blood gas machines. These machines, along with the measurement of biochemical markers by the hospital laboratory, facilitate the care of patients with severe conditions who present to the ED. However, discrepancies have been noted between the Arterial Blood Gas (ABG) analyzers in the ED and the hospital laboratory autoanalyzer in relation to electrolyte and hemoglobin measurements. The present study was performed to determine whether the ABG and laboratory measurements of potassium, sodium, and hemoglobin levels are equivalent, and whether ABG analyzer results can be used to guide clinical care before the laboratory results become available.Materials and MethodsStudy power analyses revealed that 200 consecutive patients who presented to our ED would allow this prospective single-center cohort study to detect significant differences between ABG- and laboratory-measured potassium, sodium, and hemoglobin levels. Paired arterial and venous blood samples were collected within 30 minutes. Arterial blood samples were measured in the ED by an ABL 90 FLEX blood gas analyzer. The biochemistry and blood cell counts of the venous samples were measured in the hospital laboratory. The potassium, sodium, and hemoglobin concentrations obtained by both methods were compared by using paired Student’s t-test, Spearman’s correlation, Bland-Altman plots, and Deming regression.ResultsThe mean ABG and laboratory potassium values were 3.77±0.44 and 4.2±0.55, respectively (P<0.0001). The mean ABG and laboratory sodium values were 137.89±5.44 and 140.93±5.50, respectively (P<0.0001). The mean ABG and laboratory Hemoglobin values were 12.28±2.62 and 12.35±2.60, respectively (P = 0.24).ConclusionAlthough there are the statistical difference and acceptable biases between ABG- and laboratory-measured potassium and sodium, the biases do not exceed USCLIA-determined limits. In parallel, there are no statistical differences and biases beyond USCLIA-determined limits between ABG- and laboratory-measured hemoglobin. Therefore, all three variables measured by ABG were reliable.

How closely do blood gas electrolytes and haemoglobin agree with serum values in adult emergency department patients: An observational study

“…POC blood gas analysers are available in the resuscitation area of most developed countries' ED and can provide fast data on these parameters. 3,10 Our study, the largest ED-based study, agrees with these latter studies that, when taken in clinical context, agreement is close enough to guide time critical decision-making. Some authors have regarded agreement between these methods of analysis as unacceptable and recommended caution when interpreting POC blood gas analyser results.…”

“…3 To allow for missing data and exclusions we aimed for recruitment of a minimum of 400 sample pairs. Post-hoc calculation using the standard deviations for the difference between measures found in our study and the method described by Altman 2 show that a sample size of 300 yields 95% confidence intervals around the limits of agreement of 0.4 mmol/L for sodium concentration, 0.06 mmol/L for potassium concentration and 0.9 for haemoglobin concentration.…”

Concordance between point‐of‐care blood gas analysis and laboratory autoanalyzer in measurement of hemoglobin and electrolytes in critically ill patients

“…An understanding of differences, if any, in results of the same test performed on these machines and their clinical relevance, would be crucial to ascertain the implications in clinical decision‐making. The existing literature comparing these tests yielded mixed results and use of small sample sizes, study population, and method of sampling may have contributed to the discrepancy …”

“…The existing literature comparing these tests yielded mixed results and use of small sample sizes, study population, and method of sampling may have contributed to the discrepancy. [5][6][7][8][9] We tested the hypothesis that results of the same test performed on BGA machine and AA machine have high degree of concordance in an unselected population of critical care patients and that the two test methods could be used interchangeably. To test this hypothesis, we retrospectively analyzed the concordance between the electrolyte and hemoglobin values obtained from these two test methods using the largest sample size reported to date.…”

Compatibility of Na and K Values Measured by Biochemistry Analyser And Blood Gas Analyser In Different Clinical Situations

“…Although there are several studies regarding this correlation, the aim of our study was to assess compatibility of serum sodium and potassium levels of blood gas and biochemistry laboratory analysis in different clinical situations like hypernatremia, hypokalemia etc (3,4) In this study we aimed to evaluate the correlation of serum sodium and potassium levels measured with blood gas analyser (BGA) and biochemistry laboratory autoanalyser (BLA) devices in the laboratory.…”