Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany.
Instand e.V., Düsseldorf, Germany.
Clin Chim Acta. 2018 Dec;487:318-324. doi: 10.1016/j.cca.2018.10.024. Epub 2018 Oct 17.
Poor comparability between laboratories is often observed in the measurement of HbA. A measurement procedure of higher metrological order is needed for value assignment to a reference material that shall be used as primary calibrator.
A reference measurement procedure has been developed based on isotope dilution mass spectrometry (IDMS). The α- and δ- subunits are quantified by signature peptides released by tryptic digestion of a 25 μL-blood sample. Full length U-N-labeled HbA and HbA are used as internal standards and added to the sample at concentrations closely matching the levels of the natural forms in blood. By this, an improvement in precision could be achieved with respect to previous mass-spectrometry based methods.
Recovery of HbA added to a blood sample was within 102.6-105.2%. Repeatability and within-laboratory imprecision was <2.0% for two blood samples containing HbA at a low and a high fraction. Total combined measurement uncertainty is estimated as 5.5%. Good agreement (r = 0.998) of results was obtained in a comparison of two laboratories using the described IDMS procedure. There is good correlation between commercial analytical systems and IDMS (r = 0.975-0.989). Some of the platforms provide significantly biased results, however, which potentially could be mitigated by reference to IDMS.
IDMS holds a promise to be suitable as a reference measurement procedure for standardization of HbA2-measurements in laboratory medicine.
在测量糖化血红蛋白（HbA）时，经常观察到实验室之间的可比性较差。需要一种更高计量学等级的测量程序，以便将参考物质赋值为用作主要校准器的值。
基于同位素稀释质谱法（IDMS）开发了参考测量程序。通过对 25μL 血样进行胰蛋白酶消化释放的特征肽来定量测定 α-和 δ-亚基。全长 U-N 标记的 HbA 和 HbA 用作内标，并以与血液中天然形式水平密切匹配的浓度添加到样品中。通过这种方式，可以相对于以前基于质谱的方法提高精密度。
添加到血样中的 HbA 的回收率在 102.6-105.2%之间。对于包含低和高分数 HbA 的两个血样，重复性和实验室内部不精密度均<2.0%。总合并测量不确定度估计为 5.5%。使用描述的 IDMS 程序对两个实验室进行比较时，结果具有良好的一致性（r=0.998）。商业分析系统与 IDMS 之间存在良好的相关性（r=0.975-0.989）。然而，一些平台提供的结果存在显著的偏差，但是通过参考 IDMS 可能会减轻这种偏差。
IDMS 有望成为实验室医学中糖化血红蛋白（HbA）标准化的参考测量程序。
