E. MUNDWILER¹, T. STRUJA², P. SCHÜTZ², A.R. HUBER¹, L. BERNASCONI<sup>1

1</sup>Institute of Laboratory Medicine, Kantonsspital Aarau, Switzerland, ²Medical University Department, Division of General Internal and Emergency Medicine, Kantonsspital Aarau, Aarau, Switzerland

The uncontrolled overproduction of thyroid hormones in Graves’ disease (GD) is induced by the binding of stimulating auto-antibodies to the TSH-receptor. Current methods in routine diagnostics detect total TSH-receptor antibodies (TRAb) not discriminating between stimulating or inhibiting antibodies which contrariwise lead to hypothyroidism. The newly developed IMMULITE® 2000 TSI assay from Siemens specifically identifies thyroid stimulating auto-antibodies (TSI). This study aims at comparing the sensitivity and specificity of this method with present routine assays detecting TRAb (RSR TRAb 3rd Gener. ELISA, BRAHMS TRAK human KRYPTOR). In a small scale retrospective study we measured TRAb and TSI serum levels of 30 patients diagnosed with GD and 19 control patients with other thyroid diseases. RSR TRAb reached the highest sensitivity (100%) compared to BRAHMS TRAK (69%) and IMMULITE® TSI (80%). Greatest specificity was observed for BRAHMS TRAK (100%) versus IMMULITE® TSI (94.7%) and RSR TRAb (52.6%). Despite the fact that RSR TRAb detects total antibodies it currently seems to be the most sensitive method to identify patients with Graves’ disease with the drawback of its low specificity. BRAHMS TRAK on the other hand shows high specificity but rather low sensitivity. The new IMMULITE® TSI assay reveals good diagnostic performance and is a useful tool for the identification of Graves’ disease patients.