Hormone Laboratory, Dept. Medical Biochemistry, Oslo University Hospital, Aker, PO Box 4959 Nydalen, 0424 Oslo, Norway; Biochemical Endocrinology and Metabolism Research Group, Oslo University Hospital, Aker, PO Box 4959 Nydalen, 0424 Oslo, Norway.
Hormone Laboratory, Dept. Medical Biochemistry, Oslo University Hospital, Aker, PO Box 4959 Nydalen, 0424 Oslo, Norway; Biochemical Endocrinology and Metabolism Research Group, Oslo University Hospital, Aker, PO Box 4959 Nydalen, 0424 Oslo, Norway.
Clin Biochem. 2023 Nov;121-122:110676. doi: 10.1016/j.clinbiochem.2023.110676. Epub 2023 Oct 15.
Free T4 (FT4) determination is one of the most commonly performed biochemical tests in endocrinology. Treatment of thyroid dysfunctions is adjusted based on the severity of symptoms and biochemical test results. For Graves' hyperthyroidism, clinical guidelines recommend using FT4 as a (rough) guide to dose antithyroid drugs, together with other clinical information. It is well known that different platforms and methods give different FT4 results; however, large non-linear method differences at high FT4 concentrations are less well recognized. Current clinical guidelines do not make it clear that method differences in the hyperthyroid range can affect recommendations.
Serum samples from patients with very low (biochemically hypothyroid) to very high (hyperthyroid) concentrations of FT4 and/or free T3 (FT3) were analyzed using Abbott Alinity and compared to concentrations measured using Roche Cobas, Siemens ADVIA Centaur (FT4 only) and an in-house equilibrium dialysis liquid chromatography tandem mass spectrometry (LC-MS/MS) method.
Alinity measured markedly lower FT4 and FT3 concentrations compared to the other methods, particularly at high FT4 concentrations. Regression analysis indicated that Alinity FT4 had a non-linear (curved) relationship to FT4 measured by the other methods. The method differences affected guideline-recommended treatments for hyperthyroidism.
Measured free thyroid hormone concentrations are highly method-dependent, especially at high FT4 concentrations. Clinicians treating hyperthyroid patients should be aware that patients appear much less hyperthyroid from FT4-measurements performed using Alinity compared to Cobas or Centaur. Guideline-recommended antithyroid drug dosages based on FT4 (including multiples of the upper reference range) have to be adjusted to the FT4 method used. FT4 results from different methods should be clearly distinguished (e.g. separate lines) in medical records.
游离甲状腺素（FT4）的测定是内分泌学中最常进行的生化检验之一。甲状腺功能障碍的治疗是根据症状的严重程度和生化检验结果来调整的。对于格雷夫斯病甲亢，临床指南建议使用 FT4 作为（粗略）指导抗甲状腺药物剂量的依据，同时结合其他临床信息。众所周知，不同的平台和方法会产生不同的 FT4 结果；然而，在高 FT4 浓度下，大的非线性方法差异则不太被人认识。目前的临床指南并没有明确指出，在甲亢范围内的方法差异会影响建议。
使用雅培 Alinity 分析来自 FT4 和/或游离 T3（FT3）浓度极低（生化性甲状腺功能减退）到极高（甲状腺功能亢进）的患者血清样本，并与罗氏 Cobas、西门子 ADVIA Centaur（仅 FT4）和内部平衡透析液相色谱串联质谱（LC-MS/MS）方法测量的浓度进行比较。
Alinity 测量的 FT4 和 FT3 浓度明显低于其他方法，特别是在高 FT4 浓度时。回归分析表明，Alinity FT4 与其他方法测量的 FT4 之间存在非线性（曲线）关系。方法差异影响了甲亢的推荐治疗。
所测量的游离甲状腺激素浓度高度依赖于方法，特别是在高 FT4 浓度时。治疗甲亢患者的临床医生应该意识到，与 Cobas 或 Centaur 相比，使用 Alinity 进行 FT4 测量的患者看起来要少得多甲亢。基于 FT4（包括参考范围上限的倍数）的推荐抗甲状腺药物剂量必须根据使用的 FT4 方法进行调整。不同方法的 FT4 结果应在病历中明确区分（例如，单独的线）。
