Twomey Patrick J, Viljoen Adie, Reynolds Timothy M, Wierzbicki Anthony S
Department of Clinical Biochemistry, The Ipswich Hospital, Ipswich IP4 5PD, UK.
J Trace Elem Med Biol. 2008;22(1):50-3. doi: 10.1016/j.jtemb.2007.11.001. Epub 2008 Feb 19.
Copper is an essential nutrient but is toxic when the free form is in excess. Wilson's disease (WD) is an autosomal recessive disorder of copper excess. Its diagnosis is a challenge, especially in the absence of obvious neurological changes, or Kayser-Fleischer rings. Non-ceruloplasmin-bound copper is a calculated parameter devised for the investigation of patients who potentially have WD.
We compared non-ceruloplasmin-bound copper from three different laboratories. We retrospectively reviewed paired ceruloplasmin and copper data and calculated non-ceruloplasmin-bound copper. Comparative statistics, linear regression, chi-square test and graphical techniques were employed to compare the data.
All three assays had negative results for over 20% of the non-ceruloplasmin-bound copper concentrations; this was not significantly different. However, there were statistically significant differences for the 97.5th percentile. When plotted against the ceruloplasmin and copper concentrations, significant differences existed for both the visual and linear regression data between the three different laboratories.
Non-ceruloplasmin-bound copper cut-offs may not be transferable between laboratories. Each laboratory should derive its own cut-offs for the 97.5th percentile, as there are differences due to assays, populations or both.
铜是一种必需营养素，但游离形式过量时具有毒性。威尔逊病（WD）是一种常染色体隐性铜过量疾病。其诊断具有挑战性，尤其是在没有明显神经变化或凯泽-弗莱舍尔环的情况下。非铜蓝蛋白结合铜是为调查可能患有WD的患者而设计的一个计算参数。
我们比较了来自三个不同实验室的非铜蓝蛋白结合铜。我们回顾性地分析了配对的铜蓝蛋白和铜数据，并计算了非铜蓝蛋白结合铜。采用比较统计、线性回归、卡方检验和图形技术对数据进行比较。
所有三种检测方法对超过20%的非铜蓝蛋白结合铜浓度检测结果为阴性；这一差异无统计学意义。然而，第97.5百分位数存在统计学显著差异。当与铜蓝蛋白和铜浓度作图时，三个不同实验室之间的直观数据和线性回归数据均存在显著差异。
非铜蓝蛋白结合铜的临界值可能无法在不同实验室之间通用。每个实验室都应得出自己的第97.5百分位数临界值，因为由于检测方法、人群或两者原因存在差异。
