ABSTRACT
BACKGROUND: Hyperthyroidism in Graves' disease (GD) is often associated with the production of autoantibodies (TRAb) to the thyrotropin receptor (TSHR). Current manual second generation TRAb assays demonstrate high clinical sensitivity, but are labor-intensive and time consuming. Until recently, technical difficulties prevented the availability of an automatic TRAb assay. METHODS: Development of a fast and fully automated TRAb assay on the Elecsys/cobas e electrochemiluminescence immunoassay platform. RESULTS: A labeled thyroid-stimulating human monoclonal TSHR autoantibody (M22) was used in an automated M22-binding inhibition assay. TRAb are detected by their ability to competitively inhibit M22-binding to solubilized porcine TSHR (pTSHR). High clinical sensitivity could be maintained by assembling multiple TSHR binding sites within a soluble oligomeric immunocomplex for improved TRAb binding. Requirement of sufficient on board stability of the delicate TSHR structure in solution for several days was met by pre-complexation of the pTSHR with a capture antibody to its C-terminus in combination with the use of structure-stabilizing chemical chaperones. Total imprecision coefficient of variation (CV) at 1.71 (approximate cut-off) was found to be 11.4%. TRAb results were available within 30 min. CONCLUSIONS: Availability of a fast and automatic TRAb assay offers an attractive alternative to the manual TRAb assays for the differential diagnosis of hyperthyroidism.
Subject(s)
Autoantibodies/blood , Immunoassay/methods , Receptors, Thyrotropin/immunology , Animals , Graves Disease/diagnosis , Humans , Luminescent Measurements , Protein Binding , Reagent Kits, Diagnostic , Receptors, Thyrotropin/metabolism , SwineABSTRACT
BACKGROUND: Most recently, a new rapid and fully automated electrochemiluminescence immunoassay for the determination of TSH receptor autoantibodies (TRAb) based on the ability of TRAb to inhibit the binding of a human thyroid-stimulating monoclonal antibody (M22) has been established. OBJECTIVE: To evaluate this assay system in clinical routine based on an international multicentre trial and to compare the results with other established TRAb assays. PATIENTS AND MEASUREMENTS: Totally 508 Graves' disease (GD), 142 autoimmune thyroiditis, 107 subacute thyroiditis, 109 nonautoimmune nodular goitre, 23 thyroid cancer patients and 446 normal controls were retrospectively evaluated. RESULTS: ROC plot analysis revealed an area under curve of 0.99 (95% CI: 0.99-1.0) indicating a high assay sensitivity and specificity. The highest sensitivity (99%) and specificity (99%) was seen at a cut-off level of 1.75 IU/l. Here, the calculated positive predictive value was 95%, whereas the negative predictive value was 100%. Applying the ROC plot-derived cut-off of 1.75 IU/l we found a sensitivity for TRAb positivity within the group of newly diagnosed GD patients of 97% which is in accordance to the sum of different nonautomated porcine TSH receptor-based assays with a sensitivity of 94% indicating an excellent analytical performance of the new assay format. Detailed comparison of the automated and the sum of manual assays revealed a near identical specificity. CONCLUSION: Our results demonstrate that this new assay system has a high sensitivity for detecting GD and specificity for discriminating from other thyroid diseases. This assay may represent the future technology for rapid fully automated TRAb detection.
