A Review Laboratory Advancements in Thyroid Stimulating Receptor Autoantibodies Assays: Diagnostic and Clinical Applications

Abstract

Thyroid-stimulating hormone receptor autoantibodies (TRAbs) play a crucial role in the pathophysiology of autoimmune thyroid diseases, particularly Graves' disease (GD). TRAbs can be classified into stimulating (S-TRAb), blocking (B-TRAb), and apoptotic (A-TRAb) autoantibodies based on their biological functions. Currently, two major categories of TRAb assays are utilized in clinical practice: immunoassays (TBII and IMMULITE 2000 TSI) and bioassays (TSAb). While TBII assays are widely used, they cannot differentiate antibody functionalities. The IMMULITE 2000 TSI assay offers improved sensitivity but lacks specificity. TSAb bioassays provide unparalleled sensitivity and functionality assessment, making them valuable for precise S-TRAb detection. However, variability in assay thresholds, differences in kit sources, and challenges in standardization limit their clinical applicability. Incorporating S-TRAb into standardized diagnostic frameworks and addressing assay inconsistencies are crucial for improving diagnostic precision. Beyond GD, S-TRAb assays exhibit potential in diagnosing related conditions such as Graves' ophthalmopathy, fetal and neonatal hyperthyroidism, dysthyroid optic neuropathy, and acute hyperthyroid myopathy. Further research is needed to explore the diagnostic utility, treatment guidance, and management implications of S-TRAb in these conditions. Standardization and consistency in assay methodologies are essential for establishing TSAb bioassays as reliable diagnostic tools for GD and other thyroid-related disorders.