Analytical and clinical performance of the updated Elecsys Anti-TPO II assay for the detection of antibodies against thyroid peroxidase to aid in the diagnosis of autoimmune thyroid diseases

Objectives Use of polyclonal antibodies (pAbs) in immunoassays has limitations related to inter-batch variation and supply chain stability which may affect assay reproducibility, scalability, and sustainability. The Elecsys ® Anti-TPO II assay, where the pAb of the Elecsys Anti-TPO assay has been replaced with two monoclonal antibodies, aims to address these factors. We evaluated analytical and clinical performance for Elecsys Anti-TPO II using Cobas ® e 601 and e 801 analyzers. Methods Repeatability, intermediate precision, and reproducibility were assessed over 5 days at three sites, within/between multiple reagent lots and analyzers. Method comparisons were performed against Elecsys Anti-TPO and three other immunoassays, using 218 serum samples covering the measuring range. The clinical cutoff was derived from 85 patients with confirmed Hashimoto thyroiditis (HT); reference intervals determined using samples from 230 healthy euthyroid individuals. Clinical performance was evaluated in 608 patients with confirmed HT, Graves disease, non-autoimmune thyroid diseases, or non-thyroid autoimmune diseases. Results Elecsys Anti-TPO II demonstrated high precision (standard deviations for repeatability, intermediate precision, and reproducibility <1.6 IU/mL for measurements ≤30 IU/mL; coefficients of variation <7 % for measurements >30 IU/mL) and improved semi-quantitative agreement (94.0–97.7 %) with comparator assays, vs. Elecsys Anti-TPO (88.5–90.8 %). The 95th percentile of the reference range cohort was <8 IU/mL; specificity in this cohort was 97.4 % (cutoff of ≥20 IU/mL). Clinical sensitivity for HT was 90.5 %; clinical specificity in disease control groups was 90.7 %. Conclusions Elecsys Anti-TPO II offers robust analytical and clinical performance, supporting its utility in diagnosing auto-immune thyroid diseases in routine clinical practice.