Electrolyte measurements differ between point-of-care and reference analysers in dogs with hypoadrenocorticism

Introduction: Dogs treated for hypoadrenocorticism are monitored through analysis of their blood electrolytes. This is routinely performed with point‐of‐care analysers and doses of medications are adjusted based on the results. Objectives: To investigate the performance of two point‐of‐care analysers (IDEXX Catalyst Dx and IDEXX VetStat) against a reference laboratory method for the measurement of blood sodium, potassium and chloride concentrations, as well as sodium: potassium ratios, in dogs diagnosed with and treated for hypoadrenocorticism. Methods: Forty‐eight dogs were enrolled into a prospective cross‐sectional study. Paired blood samples were taken and tested on two point‐of‐care analysers and at a reference laboratory. Statistical analysis was then performed with Bland‐Altman analysis and Passing‐Bablok regression. The clinical effects of inaccurate electrolyte analysis were investigated. Results: In total, 329 samples were tested on the Catalyst analyser, while another 72 samples were tested on the VetStat. Passing‐Bablok regression identified both proportional and constant bias for some analytes. There was poor agreement between sodium and chloride concentrations on both analysers. Both analysers tended to give higher results than the reference method for all analytes, except for potassium when measured on the VetStat. Clinical Significance: There are inherent differences between the electrolyte concentrations measured by these two point‐of‐care analysers and reference laboratory methods in dogs with hypoadrenocorticism