Clin Chem Lab Med
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Comparative Study
Salivary cortisol--an alternative to serum cortisol determinations in dynamic function tests.
Salivary cortisol was measured as an alternative to serum cortisol as a marker for adrenocortical function following insulin tolerance test, corticotropin-releasing-hormone stimulation and adreno-corticotrophic hormone stimulation. During insulin tolerance test and corticotropin-releasing-hormone stimulation adreno-corticotrophic hormone was also measured. The tests were performed on healthy control subjects as well as on patients under investigation for various disturbances in the hypothalamic-pituitary-adrenocortical axis (insulin tolerance test: 3 controls on two occasions and 14 patients; corticotropin-releasing-hormone stimulation: 4 controls and 18 patients; adreno-corticotrophic hormone stimulation: 6 controls and 10 patients). ⋯ Characteristic of the results for the insulin tolerance test was a significant initial mean decrease (p < 0.05), not found in serum, and the highest observed salivary cortisol value was delayed for at least 30 minutes compared to that in serum. Plasma adreno-corticotrophic hormone correlated significantly with the cortisol concentrations determined 15 minutes later in serum (r = 0.54-0.64) and in saliva (r = 0.76-0.85). The more pronounced cortisol response in saliva than in serum and its closer correlation with adreno-corticotrophic hormone offer advantages over serum cortisol, suggesting salivary cortisol measurement may be used as an alternative parameter in dynamic endocrine test.
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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.