Han Bingqing, Ge Menglei, Zhao Haijian, Yan Ying, Zeng Jie, Zhang Tianjiao, Zhou Weiyan, Zhang Jiangtao, Wang Jing, Zhang Chuanbao
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Clin Chem Lab Med. 2017 Nov 27;56(1):51-58. doi: 10.1515/cclm-2017-0175.
Serum calcium level is an important clinical index that reflects pathophysiological states. However, detection accuracy in laboratory tests is not ideal; as such, a high accuracy method is needed.
We developed a reference method for measuring serum calcium levels by isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS), using 42Ca as the enriched isotope. Serum was digested with 69% ultrapure nitric acid and diluted to a suitable concentration. The 44Ca/42Ca ratio was detected in H2 mode; spike concentration was calibrated by reverse IDMS using standard reference material (SRM) 3109a, and sample concentration was measured by a bracketing procedure. We compared the performance of ID ICP-MS with those of three other reference methods in China using the same serum and aqueous samples.
The relative expanded uncertainty of the sample concentration was 0.414% (k=2). The range of repeatability (within-run imprecision), intermediate imprecision (between-run imprecision), and intra-laboratory imprecision were 0.12%-0.19%, 0.07%-0.09%, and 0.16%-0.17%, respectively, for two of the serum samples. SRM909bI, SRM909bII, SRM909c, and GBW09152 were found to be within the certified value interval, with mean relative bias values of 0.29%, -0.02%, 0.10%, and -0.19%, respectively. The range of recovery was 99.87%-100.37%. Results obtained by ID ICP-MS showed a better accuracy than and were highly correlated with those of other reference methods.
ID ICP-MS is a simple and accurate candidate reference method for serum calcium measurement and can be used to establish and improve serum calcium reference system in China.
血清钙水平是反映病理生理状态的重要临床指标。然而，实验室检测的准确性并不理想，因此需要一种高精度的方法。
我们开发了一种通过同位素稀释电感耦合等离子体质谱法（ID ICP-MS）测量血清钙水平的参考方法，使用(^{42}Ca)作为富集同位素。血清用(69%)的超纯硝酸消化并稀释至合适浓度。在(H2)模式下检测(^{44}Ca/^{42}Ca)比值；使用标准参考物质（SRM）3109a通过反向同位素稀释质谱法校准加标浓度，并通过括值法测量样品浓度。我们使用相同的血清和水样，将ID ICP-MS的性能与中国其他三种参考方法的性能进行了比较。
样品浓度的相对扩展不确定度为(0.414%)（(k = 2)）。对于其中两份血清样品，重复性（批内不精密度）、中间精密度（批间不精密度）和实验室内不精密度的范围分别为(0.12%\ - 0.19%)、(0.07%\ - 0.09%)和(0.16%\ - 0.17%)。发现SRM909bI、SRM909bII、SRM909c和GBW09152在认证值区间内，平均相对偏差值分别为(0.29%)、(-0.02%)、(0.10%)和(-0.19%)。回收率范围为(99.87%\ - 100.37%)。ID ICP-MS获得的结果显示出比其他参考方法更好的准确性，并且与它们高度相关。
ID ICP-MS是一种用于血清钙测量的简单且准确的候选参考方法，可用于建立和完善中国的血清钙参考体系。
