# Microarray-Based Avidity Assay for Assessment of Thyroid Autoantibodies

## TL;DR

This study introduces a new microarray-based method to measure the strength of thyroid autoantibodies in patients with and without thyroid disease.

## Contribution

A novel hydrogel microarray-based assay was developed to assess thyroid autoantibody avidity in a multiplex format.

## Key findings

- Autoantibody avidity varied significantly between healthy carriers and patients with autoimmune thyroid disease.
- Higher avidity indices were observed in patients with thyroid neoplasm and type 1 diabetes.
- Avidity maturation of AbTPO was demonstrated over time in patients with Hashimoto’s thyroiditis.

## Abstract

Background/Objectives: The aim of this study was to evaluate the avidity of thyroid autoantibodies (Abs) in sera of patients with autoimmune thyroid disease (AITD) and thyroid autoantibody carriers without diagnosed AITD. Methods: A hydrogel microarray-based multiplex assay with the chaotrope destruction stage was developed to measure the avidity of thyroid disease-associated autoantibodies, including those targeting thyroperoxidase (TPO), thyroglobulin (Tg), and other minor antigens. Results: Evaluation of the assay in three independent cohorts of patients, totaling 266 individuals with and without AITD, demonstrated the heterogeneous avidity of autoantibodies to thyroid proteins. For the confirmation study, the median avidity index (AI) for AbTg was 29.9% in healthy autoantibody carriers, 52.6% for AITD patients, and 92.7% for type 1 diabetes (T1D) thyroid autoantibody carriers. The median AI for AbTPO was 39.9% in healthy carriers, 73.4% in AITD patients, 83.2% in T1D thyroid autoantibody carriers, and 98.5% in AITD patients with thyroid neoplasm. In patients with Hashimoto’s thyroiditis and known disease duration, changes in the avidity maturation of AbTPO over time were demonstrated. Conclusions: Longitudinal studies of TPO- and/or Tg-positive healthy individuals (with an interval of 1–2 years between visits) are needed to evaluate the maturation of autoantibody avidity during the asymptomatic phase and to assess the potential of autoantibody avidity as a prognostic marker for disease development.