Clin Chem Lab Med
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Comparative Study
Total carbon dioxide measured by the Vitros enzymatic method.
We evaluated the performance of an enzymatic method using dry chemistry for serum total carbon dioxide (tCO2) determination using a Vitros 500 analyser. Imprecision results were acceptable and the linearity was verified for concentrations within a range of 5.5-39.2 mmol/l, i.e. Y(measured) = 0.93 x(calculated) + 1.32, r = 0.99. ⋯ The data revealed a mean difference of 5.48 +/- 3.09 mmol/l between the tCO2 measurements and calculated bicarbonate. This was statistically (p = 0.01) and clinically significant. We conclude that the Vitros method provides reliable tCO2 results in venous serum but this method must not be used as an interchangeable alternative to calculated arterial bicarbonate in order to avoid confusion, misinterpretation of results and erroneous therapeutic decisions.