Ann Lab Med 2019; 39(4): 381-387
Comparison of Six Automated Immunoassays With Isotope-Diluted Liquid Chromatography–Tandem Mass Spectrometry for Total Thyroxine Measurement
Songlin Yu, M.D.1*, Weiyan Zhou, Ph.D.2*, Xinqi Cheng, M.D.1, Qinghui Meng, M.D.3, Honglei Li, B.D.1, Li’an Hou, B.D.1, Jun Lu, B.D.1, Shaowei Xie, B.D.1, Qian Cheng, B.D.1, Chuanbao Zhang, M.D.2, and Ling Qiu , M.D.1
1Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China; 2National Center for Clinical Laboratories, Beijing Hospital, National Center for Gerontology, Beijing Engineering Research Center of Laboratory Medicine, Beijing, China; 3Department of Clinical Laboratory, The Affiliated Hospital of Qingdao University, Qingdao, China
Corresponding author: Ling Qiu, M.D.
Department of Clinical Laboratory, Peking Union Medical College Hospital Chinese Academy of Medical Sciences, No. 1 Shuaifu Yuan, Dongsheng, Beijing 100730, China
Tel: +86-01069159707, Fax: +86-01069159712
*These authors contributed equally to this study.
Received: May 20, 2018; Revised: October 22, 2018; Accepted: January 29, 2019; Published online: July 1, 2019.
© Korean Society for Laboratory Medicine. All rights reserved.

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Background: Accurate serum total thyroxine (TT4) measurement is important for thyroid disorder diagnosis and management. We compared the performance of six automated immunoassays with that of isotope-diluted liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) as the reference method. We also evaluated the correlation of thyroid stimulating hormone (TSH) with TT4 measured by ID-LC-MS/MS and immunoassays.
Methods: Serum was collected from 156 patients between October 2015 and January 2016. TT4 was measured by immunoassays from Abbott (Architect), Siemens (ADVIA Centaur XP), Roche (E601), Beckman-Coulter (Dxi800), Autobio (Autolumo A2000), and Mindray (CL-1000i), and by ID-LC-MS/MS. Results were analyzed using Passing–Bablok regression and Bland–Altman plots. Minimum requirements based on biological variation were as follows: a mean bias of ≤4.5% and total imprecision (CV) of ≤3.7%.
Results: All immunoassays showed a correlation >0.945 with ID-LC-MS/MS; however, the slope of the Passing–Bablok regression line varied from 0.886 (Mindray) to 1.23 (Siemens) and the intercept from -12.8 (Siemens) to 4.61 (Mindray). Only Autobio, Beckman-Coulter, and Roche included the value of one in the 95% confidence interval for slope. The mean bias ranged from -10.8% (Abbott) to 9.0% (Siemens), with the lowest value noted for Roche (3.5%) and the highest for Abbott (-10.8%). Only Abbott and Roche showed within-run and total CV ≤3.7%.
Conclusions: Though all immunoassays correlated strongly with ID-LC-MS/MS, most did not meet the minimum clinical requirement. Laboratories and immunoassay manufacturers must be aware of these limitations.
Keywords: Immunoassay, Isotope-diluted liquid chromatography tandem mass spectrometry, Thyroxine, Evaluation, Performance

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