Külpmann W R, Maibaum P, Sonntag O
Institut für Klinische Chemie I, Medizinische Hochschule Hannover.
J Clin Chem Clin Biochem. 1990 Nov;28(11):825-33.
The reliability of electrolyte determinations with the Ektachem 700 was evaluated by various means including the use of reference method values. The influence of protein concentration, which may alter the viscosity and hence the speed of diffusion, was systematically investigated by using samples of varying protein concentration obtained by ultracentrifugation. Calcium. The mean bias between Ektachem results and reference method values of 9 control sera was -7.3%. In a comparative study with native sera a negative bias was not obtained. The accuracy was independent of the protein concentration. Chloride. The mean bias was -0.1% compared with reference method values. As might be expected, the difference between chloride values with Ektachem--using a "direct" ion-selective electrode--and determinations by coulometry increased with increasing protein concentrations. Magnesium. A negative bias (-5.0%) was obtained in accuracy control with reference method values, and to a smaller extent in a comparative study with native sera. An influence of the protein concentration on the magnesium determination was not observed. Phosphate. Accuracy control by method-dependent assigned values and a comparative study with native sera showed a positive bias. Ektachem results depend on the protein concentration. At 120 g/l protein the bias was +13.6%. Potassium. The mean bias, with respect to reference method values, was -1.2%. At high concentrations of proteins of "normal" composition, Ektachem results agree with measurements by flame atomic emission spectrometry; in paraproteinaemic sera the values are higher. Sodium. The mean inaccuracy was 3.3%, compared with reference method values. The dependence on the amount and composition of the total protein was similar to that found for potassium analysis.
采用包括参考方法值在内的多种方法，对Ektachem 700型电解质测定仪的可靠性进行了评估。通过使用超速离心获得的不同蛋白质浓度的样本，系统研究了可能改变粘度从而影响扩散速度的蛋白质浓度的影响。钙。9份对照血清的Ektachem结果与参考方法值之间的平均偏差为-7.3%。在与天然血清的对比研究中未获得负偏差。准确性与蛋白质浓度无关。氯。与参考方法值相比，平均偏差为-0.1%。正如预期的那样，使用“直接”离子选择性电极的Ektachem氯值与库仑法测定值之间的差异随着蛋白质浓度的增加而增大。镁。在与参考方法值的准确性对照中获得了负偏差（-5.0%），在与天然血清的对比研究中偏差较小。未观察到蛋白质浓度对镁测定的影响。磷。通过方法相关的指定值进行的准确性对照以及与天然血清的对比研究均显示出正偏差。Ektachem结果取决于蛋白质浓度。在蛋白质浓度为120 g/l时，偏差为+13.6%。钾。相对于参考方法值，平均偏差为-1.2%。在“正常”组成的高浓度蛋白质情况下，Ektachem结果与火焰原子发射光谱法测量结果一致；在副蛋白血症血清中，该值更高。钠。与参考方法值相比，平均误差为3.3%。对总蛋白量和组成的依赖性与钾分析中发现的情况相似。
