Agreement between sodium and potassium results measured on dry chemistry analyser and arterial blood gas analyser – A cross sectional study

Abstract

Background: Many hospitals interchangeably use the results of electrolytes performed on Laboratory Auto-analysers (LAAs) and Arterial Blood Gas analysers (ABGs). But data on comparability and validity of these measurements were ambiguous. Most of the previous studies compared electrolyte results by LAAs and ABGs, they work on the indirect ISE and direct ISE principle respectively. In this study, we have compared electrolyte results between Dry Chemistry analyser Vs. ABG analyser both works on direct ISE. Materials and Methods: We analysed 120 paired samples which were collected following exclusion criteria for electrolyte analysis on Dry chemistry analyser and ABG analyser. Bland Altman test and Lins’ concordance coefficient were performed to check the agreement between the two methods. Results from the two test methods were also assessed against the United States Clinical Laboratory Improvement Amendments (US-CLIA) 88 rules. Results: Bland Altman bias for Sodium and Potassium were -0.267(-0.88 to -0.348) and -0.097(-0.18 to 0.013) respectively. 13.3% of Sodium and 4.1% of Potassium results were outside USCLIA variation limits. Lins' concordance coefficient values for Sodium and Potassium were 0.85(0.79 - 0.89) and 0.85(0.80- 0.89). Conclusion: In the present study we found that the electrolytes, Sodium and Potassium measured on the Dry chemistry analyser showed bias of -0.3 and -0.1 compared to that of the Arterial Blood gas analyser. For both electrolyte values Lower limit of agreement (LLOA) and Upper limit of agreement (ULOA) were beyond the CLIA/ maximum allowable errors which indicate these methods cannot be used interchangeably.

Keywords

• electrolytes
• dry chemistry
• arterial blood gas analysis
• bland altman analysis
• usclia