Department of Chemical Pathology, Princess Alexandra Hospital, Brisbane 4102, Australia.
J Crit Care. 2012 Jun;27(3):326.e9-16. doi: 10.1016/j.jcrc.2011.11.003. Epub 2012 Jan 9.
We estimated the proportion of indirect ion selective electrode (ISE) plasma sodium analyses in intensive care unit (ICU) and hospital wide, exhibiting important disagreement with direct ISE results in relation to abnormal plasma protein concentrations.
Direct and indirect ISE plasma sodium measurements were performed on 346 clinical specimens selected to reflect low, normal, or high total protein concentrations. Important intermethod disagreement was defined as |4| mmol/L or higher. Results were extrapolated to a 3-month laboratory series of 48,033 indirect ISE assays, including 2877 samples from intensive care.
Intermethod sodium disagreement at |4| mmol/L or higher was predicted for 25% of ICU samples. Almost all (97%) occurred in hypoproteinemic samples where indirect tended to exceed direct ISE estimates. Hospital wide, such disagreement was projected to occur in 8% of samples, of which the majority (70%) were also hypoproteinemic.
Important disagreement between indirect and direct ISE sodium measurements may exist in up to 1 in 4 ICU specimens and 1 in 12 hospital-wide samples. The main problem is indirect ISE overestimation associated with hypoproteinemia, potentially leading to misclassifications of pseudohypernatremia and pseudonormonatremia. We recommend that hospital laboratories consider standardization using direct ISE sodium measurement.
我们评估了在重症监护病房（ICU）和全院范围内，间接离子选择性电极（ISE）等离子体钠分析的比例，这些分析与异常血浆蛋白浓度相关的直接 ISE 结果存在重要差异。
对 346 份临床标本进行直接和间接 ISE 等离子体钠测量，这些标本选择来反映低、正常或高总蛋白浓度。重要的方法间差异定义为|4|mmol/L 或更高。结果外推到一个为期 3 个月的实验室系列，共 48033 次间接 ISE 检测，包括 2877 份来自 ICU 的样本。
在|4|mmol/L 或更高的间接方法钠差异预测了 25%的 ICU 样本。几乎所有（97%）都发生在低蛋白血症样本中，间接方法往往超过直接 ISE 估计值。在全院范围内，预计这种差异将出现在 8%的样本中，其中大多数（70%）也是低蛋白血症。
间接和直接 ISE 钠测量之间可能存在高达 1/4 的 ICU 标本和 1/12 的全院范围内样本的重要差异。主要问题是间接 ISE 高估与低蛋白血症相关，可能导致假性高钠血症和假性正常钠血症的错误分类。我们建议医院实验室考虑使用直接 ISE 钠测量进行标准化。
