Ribera Ashley, Zhang Li, Ribeiro Carla, Vazquez Norma, Thonkulpitak Janet, Botelho Julianne C, Danilenko Uliana, van Uytfanghe Katleen, Vesper Hubert W
Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA, United States.
Ref4U, Laboratory of Toxicology, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
J Mass Spectrom Adv Clin Lab. 2023 Jun 23;29:9-15. doi: 10.1016/j.jmsacl.2023.06.001. eCollection 2023 Aug.
Free thyroxine (FT4) measurement is one of the most requested tests in patient care for diagnosing and treating thyroid-related illnesses. Equilibrium dialysis (ED) is considered the "gold standard" for FT4 measurement; however, several factors have a profound effect on the reliability of FT4 assays and require special consideration.
In the current study, we focused on evaluating critical factors that could contribute to reporting errors, such as adsorption of thyroxine (T4) to labware surfaces, stability of serum samples, stock solutions, and calibrator storage conditions, as well as the solvents used to prepare T4 solutions.
The adsorption of T4 in ethanolic solutions and dialysates to labware surfaces can be reduced with the careful selection of pipette tips, test tubes, and 96-well plates. Adding pH modifiers to neat T4 solutions can improve its stability. FT4 in serum samples remains stable after exposure to four freeze-thaw cycles, 5 °C for 18-20 h, or -70 °C for a minimum of three years.
The presented study has demonstrated that the loss of analyte due to pre-analytical and analytical factors during operation of the FT4 reference measurement procedure (RMP) can be minimized by careful selection of all labware for sample preparation. It was found that the accuracy and imprecision of FT4 assays can be influenced by different types of dialysis devices, but acceptable alternatives to ED membranes were identified. This study demonstrates approaches to establish a FT4 method that is independent from specific suppliers and addresses critical pre-analytical and analytical factors important for FT4 measurements.
游离甲状腺素（FT4）检测是患者护理中用于诊断和治疗甲状腺相关疾病最常要求进行的检测之一。平衡透析（ED）被认为是FT4检测的“金标准”；然而，有几个因素对FT4检测的可靠性有深远影响，需要特别考虑。
在本研究中，我们重点评估了可能导致报告错误的关键因素，如甲状腺素（T4）在实验室器具表面的吸附、血清样本的稳定性、储备溶液和校准物的储存条件，以及用于制备T4溶液的溶剂。
通过仔细选择移液器吸头、试管和96孔板，可以减少乙醇溶液和透析液中T4在实验室器具表面的吸附。向纯T4溶液中添加pH调节剂可以提高其稳定性。血清样本中的FT4在经历四次冻融循环、在5°C下放置18 - 20小时或在-70°C下放置至少三年后仍保持稳定。
本研究表明，在FT4参考测量程序（RMP）操作过程中，通过仔细选择所有用于样品制备的实验室器具，可以将由于分析前和分析因素导致的分析物损失降至最低。发现不同类型的透析装置会影响FT4检测的准确性和不精密度，但已确定了可替代ED膜的可接受方案。本研究展示了建立一种独立于特定供应商的FT4方法的途径，并解决了对FT4测量重要的关键分析前和分析因素。
