Diagnostic testing for Graves' or non-Graves' hyperthyroidism: A comparison of two thyrotropin receptor antibody immunoassays with thyroid scintigraphy and ultrasonography.

Thyroid scintigraphy remains the most accurate method to differentiate causes of thyrotoxicosis. However, TRAb assays can be alternatively adopted in this setting, limiting the use of thyroid scintigraphy (TcTU evaluation) to TRAb-negative patients. Thyoid US is less accurate than both TRAb/TSI and thyroid scintigraphy, but the 'thyroid inferno' pattern provides a high PPV for GD.