Evaluation of two benchtop blood gas analyzers for measurement of electrolyte concentrations in venous blood samples from dogs

To assess agreement between 2 benchtop blood gas analyzers developed by 1 manufacturer (BGA 1 and BGA 2 [a newer model with reduced maintenance requirements]) and a reference chemistry analyzer for measurement of electrolyte (sodium, chloride, and potassium) in blood samples from dogs. 17 healthy staff- and student-owned dogs and 23 client-owned dogs admitted to an emergency and intensive care service. Blood collected by venipuncture was placed in lithium heparin-containing tubes. Aliquots were analyzed immediately with each BGA. Samples were centrifuged, and plasma was analyzed with the reference analyzer. Results for each BGA were compared with results for the reference analyzer by Passing-Bablok regression analysis. Percentage differences between BGA and reference analyzer results were compared with published guidelines for total allowable error. Proportional bias was detected for measurement of chloride concentration (slope, 0.7; 95% CI, 0.7 to 0.8), and constant positive bias was detected for measurement of chloride (y-intercept, 34, mmol/L; 95% CI, 16.9 to 38 mmol/L) and potassium (y-intercept, 0.1 mmol/L; 95% CI, 0.1 to 0.2 mmol/L) concentrations with BGA 1. There was no significant bias for measurement of potassium or chloride concentration with BGA 2 or sodium concentration with either BGA. Differences from the reference analyzer result exceeded total allowable error guidelines for ≥ 1 sample/analyte/BGA, but median observed measurement differences between each BGA and the reference analyzer did not. Good agreement with reference analyzer results was found for measurement of the selected electrolyte concentrations in canine blood samples with each BGA.