Clinical Value of Thyrotropin Receptor Antibodies for the Differential Diagnosis of Interferon Induced Thyroiditis.

Objective: The clinical value of thyrotropin receptor antibodies for the differential diagnosis of thyrotoxicosis induced by pegylated interferon-alpha remains unknown. We analyzed the diagnostic accuracy of thyrotropin receptor antibodies in the differential diagnosis of thyrotoxicosis in patients with chronic hepatitis C (CHC) receiving pegylated interferon-alpha plus ribavirin.

Methods: Retrospective analysis of 274 patients with CHC receiving pegylated interferon-alpha plus ribavirin. Interferon-induced thyrotoxicosis was classified according to clinical guidelines as Graves disease, autoimmune and non- autoimmune destructive thyroiditis.

Results: 48 (17.5%) patients developed hypothyroidism, 17 (6.2%) thyrotoxicosis (6 non- autoimmune destructive thyroiditis, 8 autoimmune destructive thyroiditis and 3 Graves disease) and 22 "de novo" thyrotropin receptor antibodies (all Graves disease, 2 of the 8 autoimmune destructive thyroiditis and 17 with normal thyroid function). The sensitivity and specificity of thyrotropin receptor antibodies for Graves disease diagnosis in patients with thyrotoxicosis were 100 and 85%, respectively. Patients with destructive thyroiditis developed hypothyroidism in 87.5% of autoimmune cases and in none of those with a non- autoimmune etiology (p<0.001).

Conclusions: Thyrotropin receptor antibodies determination cannot replace thyroid scintigraphy for the differential diagnosis of thyrotoxicosis in CHC patients treated with pegylated interferon.