Cut-Off Value of Thyrotropin-Receptor Antibodies in Grave’s Disease in Basrah

Background: The diagnosis of Grave's disease (GD) poses a challenge. Thyrotropin-receptor antibodies (TRAb) are the key diagnostic feature of GD, as the American and European Thyroid Associations suggested. Aim of the study: This study aims to find a cut-off level of TRAb in GD in Basrah. Methods: This is a retrospective study that included 617 patients with hyperthyroidism (530 GD and 87 non-Grave's disease (NGD) (thyroiditis or subclinical hyperthyroidism)). The candidates were patients presenting with hyperthyroidism who were referred for TRAb assay, while patients with thyroid carcinoma or nodular thyroid disease, pregnant ladies, and patients who were treated were excluded. Results: The manufacturer cut-off value of 1.75 IU/L had a sensitivity of 88.1%, specificity of 72.4%, positive predictive value (PPV) of 95.1%, and negative predictive value (NPV) of 50.0%. Our data analysis through receiver operating characteristic (ROC) statistics revealed that the optimum cut-off point with the highest total sensitivity and specificity was determined to be 3.95 IU/L, as it had a sensitivity of 76.9%, specificity of 98.8%, PPV of 99.7%, NPV of 41.3%. Conclusion: For a more accurate diagnosis of GD, the findings of the present study support the implementation of a higher TRAb cut-off value (3.95 IU/L) than that predefined by the manufacturer (1.75 IU/L).