Abstract Background Thyroglobulin (Tg) is a protein produced by the thyroid follicular cells where it acts as a substrate for thyroxine (T4) and triiodothyronine (T3) synthesis and storage for inactive forms of thyroid hormone and iodine. Tg is present in the serum of healthy individuals and can be elevated in some disorders, including autoimmune Hashimoto’s thyroiditis and Graves’ disease. Tg has an important role in monitoring patients with differentiated thyroid cancer following total thyroidectomy with or without radioiodine ablation, where Tg should become undetectable. Serial determinations are required and compared to the postsurgical baseline Tg result when possible. Evaluation of increasing Tg levels over time are more clinically important. In some patients a limiting factor in the use of serum Tg measurements is the presence of Tg autoantibodies (anti-Tg). Anti-Tg can interfere with Tg measurements causing falsely high or falsely low values. Anti-Tg should be quantitatively assessed with every measurement of serum Tg. This study evaluated the analytical performance of Atellica IM Thyroglobulin (Tg) and Anti-Thyroglobulin II (aTgII) assays on the Atellica CI Analyzer. The Atellica CI Analyzer is an automated, mid-throughput integrated chemistry and immunoassay analyzer employing both Atellica CH and Atellica IM assays. Methods Precision studies were performed per CLSI EP05-A3 using native human serum and quality control samples. Repeatability and within-lab precision samples were tested in duplicate/run, 2 runs/day for 20 days (n=80) using one reagent lot and two analyzers. Reproducibility samples were assayed in five replicates/run, 1 run/day for 5 days using three lots on three analyzers (n=225). Method comparison (MC) studies compared assay performance on Atellica IM and Atellica CI analyzers using singlicate native human serum and contrived samples (n100) and three lots per CLSI EP09c-ED3. Limit of blank, detection, and quantitation (LoB, LoD, and LoQ) samples were tested on three reagent lots and one analyzer per CLSI EP17-A2. Linearity studies tested 10 levels of mixed high, and low samples (n=5/level) over 1 day for three lots per CLSI EP06-ED2. Results Tg repeatability was 0.9–4.7%CV and within lab, 2.8–10.8% at 0.088–128.784 ng/mL (0.133–195.108 pmol/L). Tg reproducibility was =5.9%CV at =0.451 ng/mL (0.683 pmol/L) and 0.0169 ng/mL (0.0256 pmol/L) SD at 0.089 ng/mL (0.135 pmol/L). aTgII repeatability was 2.3–5.3%CV and within lab 3.1–6.2%CV at 8.1–840.3 IU/mL; aTgII reproducibility was 8.8%CV at 5.0 IU/mL and 13.8%CV at 2.4 IU/mL. MC Weighted Deming regression equations were y=1.02x-0.033 ng/mL (y=1.02x-0.050 pmol/L) at 0.074–148.115 ng/mL (0.112–224.394 pmol/L) (Tg) (r=0.998), and y=1.01x-0.1 IU/mL at 2.1–892.1 IU/mL (aTgII) (r=0.998). LoB, LoD, and LoQ were 0.036, 0.046, 0.050 ng/mL (0.055, 0.070, 0.076 pmol/L) (Tg), and 0.6, 1.0, and 1.3 IU/mL (aTgII). Linear range was 0.050–150.000 ng/mL (0.076–227.250 pmol/L) (Tg) and 1.3–1000 IU/mL (aTgII). Analytical study results on the Atellica CI Analyzer demonstrated similar performance to claims for the Atellica IM Analyzer. Conclusion Evaluation of the Atellica IM Tg and aTgII assays using the Atellica CI Analyzer demonstrated acceptable analytical performance and acceptable concordance compared to the Atellica IM analyzer.
Quintanilla et al. (Wed,) studied this question.
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