Meng Fanwen, Jonklaas Jacqueline, Leow Melvin Khee-Shing
National Healthcare Group, Department of Health Services and Outcomes Research, 3 Fusionopolis Link, Nexus@One-North, Singapore 138543, Singapore.
Division of Endocrinology, Department of Medicine, Georgetown University, 4000 Reservoir Road NW, Washington, DC 20057, USA.
Biology (Basel). 2021 Jan 11;10(1):45. doi: 10.3390/biology10010045.
Clinicians often encounter thyroid function tests (TFT) comprising serum/plasma free thyroxine (FT4) and thyroid stimulating hormone (TSH) measured using different assay platforms during the course of follow-up evaluations which complicates reliable comparison and interpretation of TFT changes. Although interconversion between concentration units is straightforward, the validity of interconversion of FT4/TSH values from one assay platform to another with different reference intervals remains questionable. This study aims to establish an accurate and reliable methodology of interconverting FT4 by any laboratory to an equivalent FT4 value scaled to a reference range of interest via linear transformation methods. As a proof-of-concept, FT4 was simultaneously assayed by direct analog immunoassay, tandem mass spectrometry and equilibrium dialysis. Both linear and piecewise linear transformations proved relatively accurate for FT4 inter-scale conversion. Linear transformation performs better when FT4 are converted from a more accurate to a less accurate assay platform. The converse is true, whereby piecewise linear transformation is superior to linear transformation when converting values from a less accurate method to a more robust assay platform. Such transformations can potentially apply to other biochemical analytes scale conversions, including TSH. This aids interpretation of TFT trends while monitoring the treatment of patients with thyroid disorders.
临床医生在随访评估过程中经常遇到甲状腺功能测试（TFT），其中包括使用不同检测平台测量的血清/血浆游离甲状腺素（FT4）和促甲状腺激素（TSH），这使得TFT变化的可靠比较和解读变得复杂。尽管浓度单位之间的相互转换很简单，但将FT4/TSH值从一个检测平台转换到另一个具有不同参考区间的平台时，这种转换的有效性仍然存在疑问。本研究旨在建立一种准确可靠的方法，通过线性变换方法将任何实验室的FT4相互转换为一个按感兴趣的参考范围进行缩放的等效FT4值。作为概念验证，通过直接模拟免疫测定、串联质谱和平衡透析同时检测FT4。线性变换和分段线性变换在FT4跨尺度转换方面都证明相对准确。当将FT4从更准确的检测平台转换到不太准确的检测平台时，线性变换表现更好。反之亦然，即当将值从不太准确的方法转换到更可靠的检测平台时，分段线性变换优于线性变换。这种转换可能适用于其他生化分析物的尺度转换，包括TSH。这有助于解释甲状腺疾病患者治疗监测期间的TFT趋势。
