Reliability of the thyroid stimulating hormone receptor antibodies level determination in diagnosing and prognosing of immunogenic hyperthyroidism

Abstract

Background/Aim. Graves disease (GD) is defined as hyperthyroidism with diffuse goiter caused by immunogenic disturbances. Antibodies to the thyroid stimulating hormone (TSH) receptors of thyroid gland (TRAb) have crucial pathogenetic importance in the development and maintenance of autoimmune hyperthyroidism. The aim of this study was to identify sensitivity, specificity, positive an negative predictive value of TRAb level in sera of patients with GD as well as to estimate significance of TRAb level for remission and GD relapses occurrence. Methods. We studied prospectively and partly retrospectively 149 patients, 109 female and 40 male patients, 5-78 years old, in the period 1982-2007. There were 96 patients with GD. The control group consisted of 53 patients, 21 with hyperthyroidism of second etiology and 32 patients on amiodarone therapy, with or without thyroid dysfunction TRAb was measured by radioreceptor assay (TRAK Assay and DYNO Test TRAK Human Brahms Diagnostica GMBH). Results. According to the results the sensitivity (Sn) of TRAb test was 80%, specificity (Sp) 100%, positive predictive value (PP) 100% and negative predictive value (NP) 83%. Also, the Sn of hTRAb test was 94%, Sp 100%, PP 100% and NP 94%. Our results show that an increased level of TRAb/hTRAb at the beginning of the disease and the level at the end of medical therapy is associated with an increased number of GD relapses and a shorter remission duration. Conclusion. Detection and measurement of TRAb in serum is a very sensitive method for diagnosing GD and very highly specific in vitro method for differential diagnosis of various forms of hyperthyroidism. Clinical significance of differentiating various forms of hyperthyroidism, using this in vitro assay, lays in adequate therapeutic choice for these entities.