19 Oct 2020
Study published in Journal of Small Animal Practice shows inherent differences between the electrolyte concentrations measured by point-of-care analysers and reference laboratory methods in dogs with hypoadrenocorticism.
Vet Times
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A study has highlighted inherent differences between the electrolyte concentrations measured by point-of-care analysers and reference laboratory methods in dogs with hypoadrenocorticism.
The study – “Electrolyte measurements differ between point-of-care and reference analysers in dogs with hypoadrenocorticism”, published in the Journal of Small Animal Practice (JSAP) – looked at the performance of two point-of-care analysers (IDEXX Catalyst Dx and IDEXX VetStat).
These were measured against a reference laboratory method for the measurement of blood sodium, potassium and chloride concentrations, as well as sodium-to-potassium ratios, in dogs diagnosed with and treated for hypoadrenocorticism.
A prospective cross-sectional study at the University of Glasgow had 48 dogs with hypoadrenocorticism enrolled, and 329 paired samples were measured on the Catalyst analyser and by the reference lab method, called ion selective electrode (ISE). A further 72 paired samples were tested on the VetStat analyser and by ISE.
Sam Fowlie, corresponding author for the paper, said: “Our results indicate that the sodium, potassium and therefore the sodium-to-potassium ratios, as well as the chloride concentrations measured by the Catalyst and VetStat analysers, may not be used interchangeably with those from a reference laboratory analyser using an indirect ISE method.
“Both analysers tended to give higher results than the reference method for all analytes, except for potassium when measured on the VetStat.”
The clinical relevance of the disagreement between the methods was investigated by assessing how often the point-of-care analysers produced results that fell outside their reference range when the ISE method found them to be within reference and vice versa.
For the Catalyst, 21 cases (6%) had discordant sodium results, 27 cases (8%) discordant potassium results and 46 cases (14%) discordant chloride results. The VetStat, meanwhile, produced results that disagreed with the ISE method in 19 cases (26%) for sodium, 3 cases (4%) for potassium measurement and 9 cases (13%) for chloride analysis.
JSAP editor Nicola Di Girolamo added: “This study reveals significant systematic differences (“bias”) between the three analysers in this study. Comparing numerical results from different analytical methods – be they point-of-care or reference laboratories – can be dangerous for patients.
“Clinicians should always use method specific thresholds and, if these are not available (for example the sodium-to-potassium ratios on some analysers), then they should exercise greater caution in their interpretation.”
