ObjectiveTo evaluate whether thyroglobin (Tg) value by radioimmunoassay (Tg-RIA) can be used as a complementary marker in differentiated thyroid cancer (DTC) patients, as serum Tg value is the key marker for the follow-up of patients with DTC, and endogenous antithyroglobulin (TgAb) interferes with serum Tg value by immunometric assay (Tg-IMA).
MethodsFifty-five in-hospital patients with DTC after total thyroidectomy and 131I ablation during September and December 2012 were enrolled. Tg-IMA tests and Tg-RIA tests were performed separately. Diagnostic criteria about relapse, metastasis or disease-free status of thyroid carcinoma were established by serum Tg, diagnostic whole body scan (D-WBS), neck ultrasonography, chest CT and patients' history.
ResultsTwo DTC patients showed false negative Tg-IMA and true positive Tg-RIA. Five patients had false negative Tg-RIA because of low sensitivity of RIA. Four patients with weak positive Tg-IMA (1.07-4.09 μg/L) required follow-up. Among the 11 DTC patients with strong TgAb positivity (>115 kU/L), two patients with positive Tg-IMA and positive Tg-RIA received second operation or radioiodine therapy, seven patients had positive Tg-RIA and negative Tg-IMA. Five of the seven patients with strong positive TgAb needed further follow-up, and two of them received radioiodine therapy.
ConclusionTg value with radioimmunoassay is a complementary marker to find false negative Tg-IMA in follow-up patients with DTC.
