Evaluation of an electrolyte analyser for measurement of concentrations of ionized calcium and magnesium in cats.

The goal of this study was to evaluate the Nova CRT 8 electrolyte analyser for determination of concentrations of ionized calcium (Ca(i)) and magnesium (Mg(i)) in cats, to determine the effects of sample handling and storage and to establish reference ranges. The precision and analytical accuracy of the Nova CRT 8 analyser were good. The concentrations of Ca(i) and Mg(i) were significantly lower in aerobically handled serum samples than in those handled anaerobically. The concentrations of Ca(i) and Mg(i) differed significantly among whole blood, plasma and serum. In anaerobically handled serum, the concentration of Ca(i) was stable for 8 h at 22 degrees C, for 5 days at 4 degrees C and for 1 week at -20 degrees C. The concentration of Mg(i) was stable for 4 h at 22 degrees C but for less than 24 h at 4 degrees C and for less than 1 week at -20 degrees C. In serum from 36 cats, the reference ranges were 1.20-1.35 mmol/L for Ca(i) and 0.47-0.59 mmol/L for Mg(i). The Nova CRT 8 electrolyte analyser is suitable for determination of Ca(i) and Mg(i) concentrations in cats. Anaerobically handled serum samples are recommended and, stored at room temperature, they yield accurate results when analysed within 4 h.