PREDICTING THE COURSE OF GRAVES´ ORBITOPATHY AND GRAVES DISEASE BY ANTI-TSH-RECEPTOR AUTOANTIBODY MEASUREMENTS- BINDING ASSAYS VERSUS FUNCTIONAL BIOASSAY
- Simon D. Lytton, Germany
Abstract
Background and Aims
The automated electrochemical luminescence immunoassays (ECLIA) of TSH receptor autoantibody binding (TRAb) and the functional measurements of stimulating and blocking TSH-receptor autoantibodies by cAMP reporter commercial cell-based bioassay have vastly improved the efficiency of Graves Disease-Orbitopathy (GD-GO) diagnosis. The aim of this study was to investigate the potential of the the funcational bioassay versus the TRAb ECLIA to predict remission or relapse of hyperthyroidism and GD-GO during the course of antithyroid drug therapy.
Methods
Biobank serum of GD-GO patients (n=254) at 24 month relapse vs remission of hyperthyroidism and 12 month mild versus severe eye inflammation were evaluated in TRAb Elecys® (Cobas Roche) and TRAb bridge assay (IMMULITE ®, Siemens) ECLIA. TSH-receptor stimulating immunoglobulins (TSAb) were assessed in the cell-based bioassay (Thyretain ®, Quidel).
Results
The predictive potentials of the TRAb ECLIA and the bioassay did not markedly differ. More than half of the patients with relapsing hyperthyroidism were identified according to high TRAb values at 6 months after the beginning of ATD. At all measured timepoints the cell-based bioassay was most sensitive – and still positive 13-16 months after the diagnosis of GD in 90% of the patients compared with ECLIA; 70% (Immulite) and 65% (Elecys).
Conclusions
The predictability of relapse vs remission of hyperthyroidism or mild vs severe GO is 50-60% and independent of anti-TSH-R assay technology at six months. Thyretain®Bioassay shows highest diagnostic sensitivity ( >80%, 2 yrs). Patients whom test within the risk range (> cut-off) are recommended to undergo intensified treatment of orbital inflammation by immunomodulatory drug and/or steroids.