Interlaboratory Reference Change Values for Thyroid Function Indicators Across Analytical Systems: A Comparative Analysis

• Published in: International journal of clinical practice (Esher) Vol. 2025; no. 1
• Main Authors: Huang, Ying, Zhang, Yan, He, Dahai, Xie, Yehong, Xu, Xiaohua, Zhou, Chaoqiong, Yuan, Dian, Kong, Lirui
• Format: Journal Article
• Language: English
• Published: London John Wiley & Sons, Inc 01.01.2025; Wiley
• Subjects: Comparative analysis; Interoperability; Laboratories; Medical laboratories; Quality control; Statistical analysis; Thyroid diseases; Thyroid gland; Thyroid hormones; Thyroid-stimulating hormone; Thyroxine; Triiodothyronine; Variation; China
• ISSN: 1368-5031; 1742-1241
• DOI: 10.1155/ijcp/6664598

Background: The clinical application of reference change values (RCVs) is primarily used within the same laboratory analytical system, with limited research addressing its application across different analytical systems in various laboratories. The aim of this study is to estimate the analytical variation (CV A ) and interlaboratory reference variation values (IL‐RCV) using external quality assessment (EQA) data and biological variation data, to assess the interoperability of test results for thyroid function indicators across laboratories, and to provide reliable information for clinicians. Methods: Data for thyroid function indicators, including thyroid‐stimulating hormone (TSH), triiodothyronine (T 3 ), thyroxine (T 4 ), free T 3 (FT 3 ), and free T 4 (FT 4 ), were obtained from eight analytical systems participating in the first EQA conducted by the Clinical Laboratory Center of the National Health Commission in the United States in 2022. The average coefficient of variation (CV) from the five quality control materials was used to determine the CV A of each indicator across laboratories. Within‐subject variation (CV I ) and between‐subject biological variation (CV G ) data were obtained on the European Federation of clinical Chemistry and Laboratory Medicine (EFLM) biological variation website. IL‐RCV values for each indicator with 95% (bilateral) probability were calculated using the log‐normal method and the application of these values between laboratories was evaluated. Results: The coefficients of CV A of thyroid function indicators differ across various analytical systems, with 27 individual items having a CV A greater than the Analyze Performance Specification target values (7%), and the overall range spanning from 3.08% to 11.85%. In addition to TSH and Abbott’s T 3 , the average CV A for all the tests exceeded the estimated data from the EFLM website. With 95% bilateral probability, the positive IL‐RCV (IL‐RCVpos) ranged from 17.7% to 68.4%, while the negative IL‐RCV (IL‐RCVneg) ranged from −15.0% to −40.6%, with the percentage of IL‐RCVpos is higher than that of IL‐RCVneg. Conclusions: There are differences in the CV A of thyroid function indicators across different analytical systems, and the IL‐RCV is not comparable. Clinicians should pay attention when interpreting reports and it is recommended to use analytical systems from the same manufacturer for the management and follow‐up of patients with thyroid diseases.