The utility of radioiodine uptake and thyroid scintigraphy in the diagnosis and management of hyperthyroidism

Abstract

The value and practice of thyroid radionuclide imaging in the diagnosis and management of hyperthyroidism is unsettled. Our objectives were to determine the influence of thyroid uptake and scintigraphy on the diagnosis of hyperthyroidism and the prediction of outcome following radioiodine therapy. We reviewed records and scintigraphic studies on 881 hyperthyroid patients carried out between 2000 and 2007. The agreement between the clinical and scintigraphic diagnosis was evaluated by kappa statistics. We determined the relationship between 4-h (123)I uptake and the outcome of (131)I treatment in 626 patients. A multiple logistic regression model was used to determine variables influencing treatment outcome in 1 year. The diagnostic categories were Graves' disease (GD, n = 383), toxic multinodular goitre (n = 253), solitary toxic nodule (n = 164) and Graves' disease coexisting with nodules (n = 81). The mean age of the patients was 58 +/- 17, (M:F 160:721). There was good agreement between clinical and scintigraph diagnosis (K = 0.60, 95% CI 0.57-0.64, P < 0.001); and they were correctly matched in 74%; mismatched in 6% and indeterminate in 20% of patients. Treatment outcome was not associated with scintigraph diagnosis (P = 0.98) or radioiodine uptake at 4 h (P = 0.2). The use of antithyroid medications before treatment predicted treatment failure (odds ratio 2.0, 95% CI 1.2-3.6, P = 0.01). Thyroid scintigraphy and uptake studies did not influence diagnosis or treatment outcomes in most cases of hyperthyroidism. Our findings in this retrospective study do not justify their routine use. Selective scanning will reduce cost and exposure to radioisotopes without compromising diagnostic accuracy or treatment outcomes.