Clinical Utility of Thyroglobulin Antibody (TgAb) Measurements for Patients with Differentiated Thyroid Cancers (DTC)

Abstract

Thyroglobulin autoantibodies (TgAb) are primarily measured in serum in conjunction with thyroglobulin (Tg)--the primary tumor marker used to monitor patients with differentiated thyroid cancers (DTC). Every specimen needs TgAb testing to authenticate that the Tg measurement is not compromised by TgAb interference. When present, TgAb concentrations per se can be monitored as a surrogate tumor marker. The aims of the study were: 1) to review published reports concerning whether there are associations between DTC, thyroid autoimmunity (Hashimoto's thyroiditis), and the presence of TgAb; and 2) to evaluate the methodological factors that influence TgAb interference with serum Tg testing. PubMed was used to identify studies published over the last 55 yr that focused on DTC relationships with thyroid autoimmunity and the presence of thyroid autoantibodies. Many studies have reported significant associations between papillary thyroid cancer and Hashimoto's thyroiditis that may have a favorable prognostic significance. TgAb is detected in approximately 20% of DTC patients and may be a more specific thyroid tumor marker than thyroid peroxidase antibodies. TgAb interferes with Tg immunometric assay (IMA) measurements, causing falsely low/undetectable Tg values, especially when TgAb concentrations are high and serum Tg concentrations (measured by RIA) are low. TgAb concentrations respond to changes in Tg-secreting thyroid tissue such that the TgAb trend can be used as a more reliable surrogate DTC tumor marker than Tg IMA. Current TgAb assays may not always detect interfering TgAb because of insensitivity and specificity differences. It is critical to retain the same method for long-term TgAb monitoring. Patients with Hashimoto's thyroiditis frequently have TgAb detected and may have a higher risk for papillary thyroid cancer. Although TgAb interferes with Tg IMA measurements, TgAb trends can be used as a surrogate DTC tumor marker in preference to Tg IMA, provided that the same method is used.