Maternal TSH-receptor antibodies predict fetal/neonatal hyperthyroidism in pregnancies with a history of Graves’ disease

Trimester-specific TRAb thresholds were higher than the universal ULN multipliers commonly applied in clinical practice, and differed by gestational age and disease status. Application of a single ULN-based threshold titer across different TRAb assays may result in misclassification (i.e. overestimation of fetal and neonatal Graves' disease) and consequently in unnecessary and resource-intensive fetal surveillance. This indicates that TRAb thresholds are assay-specific and require platform-specific clinical validation, even when assays are calibrated against a common international standard.