Laboratory for Analytical Chemistry, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
Laboratory of Reference Material Institute for Clinical Chemistry Standards (ReCCS), Kawasaki, Kanagawa, Japan.
Clin Chem Lab Med. 2011 Aug;49(8):1275-1281. doi: 10.1515/CCLM.2011.639. Epub 2011 Jun 16.
The IFCC Working Group for Standardization of Thyroid Function Tests proposes a candidate international conventional reference procedure (RMP) for measurement of the amount-of-substance concentration of free thyroxine in plasma/serum at physiological pH 7.40 and temperature (37.0°C). The unit for reporting measurement results is, by convention, pmol/L. The RMP is based on equilibrium dialysis isotope dilution-liquid chromatography/tandem mass spectrometry (ED-ID-LC/tandem MS). The rationale for proposing a conventional RMP is that, because of the physical separation step, it is unknown whether the measurement truly reflects the concentration of free thyroxine (FT4) in serum. Therefore, the ED part of the RMP has to strictly adhere to the following conditions: use of a dialysis buffer with a biochemical composition resembling the ionic environment of serum/plasma as closely as possible; buffering of the sample to a pH of 7.40 (at 37.0°C) before dialysis, however, without additional dilution; dialysis in a device with a dialysand/dialysate compartment of identical volume and separated by a membrane of regenerated cellulose and adequate cut-off; thermostatic control of the temperature during dialysis at 37.0°C±0.50°C. The convention does not apply to the ID-LC/tandem MS part, provided it is eligible to be nominated for review by the Joint Committee for Traceability in Laboratory Medicine. Here, we describe the ED procedure, inclusive its validation and transferability, in greater detail. We recommend a protocol for successful calibration, measurement and monitoring of the accuracy/trueness and precision of the candidate conventional RMP. For details on our ID-LC/tandem MS procedures, we refer to the Supplement.
国际临床化学联合会甲状腺功能检测标准化工作组提议建立候选国际常规参考程序（RMP），用于测量生理 pH 值 7.40 和温度（37.0°C）下血浆/血清中游离甲状腺素的物质浓度。报告测量结果的单位，根据惯例，为 pmol/L。RMP 基于平衡透析同位素稀释-液相色谱/串联质谱法（ED-ID-LC/串联 MS）。提议常规 RMP 的基本原理是，由于存在物理分离步骤，因此无法确定测量结果是否真实反映了血清中游离甲状腺素（FT4）的浓度。因此，RMP 的 ED 部分必须严格遵守以下条件：使用尽可能接近血清/血浆离子环境生化组成的透析缓冲液；在透析前将样品缓冲至 pH 值 7.40（37.0°C），但无需额外稀释；在体积相同且由再生纤维素制成的膜隔开的透析设备中进行透析；在 37.0°C±0.50°C 下进行透析时进行恒温控制。该惯例不适用于 ID-LC/串联 MS 部分，只要它有资格被提名接受实验室医学溯源性联合委员会的审查。在这里，我们更详细地描述了 ED 程序，包括其验证和可转移性。我们建议了一个成功校准、测量和监测候选常规 RMP 的准确性/真实性和精密度的协议。有关我们 ID-LC/串联 MS 程序的详细信息，请参考补充材料。
