Poster Presentation ESA-SRB 2023 in conjunction with ENSA

Method validation and trueness estimation of thyroglobulin by LC-MS/MS. (#234)

Chris Hodgkins 1 , Maria Charan 1 , Peter Ward 1 , Lucy Ding 1 , Douglas Chesher 1 , Cameron Wood 1
  1. NSW Health Pathology, St Leonards, NSW, Australia

Introduction

Accurate quantification of serum thyroglobulin (TG) is crucial for monitoring patients after treatment for Differentiated Thyroid Carcinoma (DTC). However, challenges arise from potential interference by Thyroglobulin Abs (TGAB) with immunoassays (IA), leading to potentially falsely low or negative results in TG measurements. Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) has emerged as a reliable analytical technique offering high sensitivity and specificity for TG measurement, addressing limitations associated with traditional IA methods.

Methods

An LC-MS/MS method was developed based on a published, validated clinical TG mass spectrometry (TG-MS) assay1, with minor adjustments to sample preparation and instrument settings made to suit local laboratory infrastructure.

Sufficient analyses were conducted to meet the criteria for “pre-validation”2, demonstrating the local TG-MS assay’s suitability in terms of sensitivity, linearity, and precision for full analytical and clinical validation.

In this study, we present the early stages of method validation and trueness estimation for TG quantification using LC-MS/MS, with thyroglobulin standardised to the Roche Cobas E601 assay using TGAB-negative human serum pools.

 

Results

A cohort of TGAB negative patient samples analysed by both IA and LC-MS/MS showed good concordance in both Passing-Bablok and Bland-Altman comparisons, with bias <5%.

In a cohort of TGAB positive samples, LC-MS/MS consistently measured higher Tg values than IA and correlation was overall poor.

When TGAB positive and TGAB negative samples were mixed before analysis, TG-MS demonstrated closer alignment to the theoretical concentration than IA.

 

Conclusion

Quantification of TG by LC-MS/MS addresses the challenges posed by positive TGAB, providing accurate and precise TG measurement in the context of DTC. The demonstrated robustness and reliability of this LC-MS/MS-based assay, establish it as a suitable tool for routine clinical use, supporting informed clinical decision-making in the management of DTC patients.

  

  1. 1. Shi, J, Phipps, WS, Owusu, BY, Henderson, CM, Laha, TJ, Becker, JO, Razavi, M, Emrick, MA, Hoofnagle, AN. A distributable LC-MS/MS method for the measurement of serum thyroglobulin. Journal of Mass Spectrometry and Advances in the Clinical Lab. 2022, 26, 28-33.
  2. 2. Grant, RP, Rappold, BA, 5 - Development and Validation of Small Molecule Analytes by Liquid Chromatography-Tandem Mass Spectrometry. In Principles and Applications of Clinical Mass Spectrometry, Rifai, N.; Horvath, A. R.; Wittwer, C. T., Eds. Elsevier: 2018; pp 115-179.