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.
ObjectiveTo compare the diagnostic efficacy of serum thyroglobulin (Tg), diagnostic 131I whole-body scan (D-WBS), neck ultrasound for diagnosing metastasis and recurrence of differentiated thyroid carcinoma (DTC). MethodsFrom May to June 2011, fifty follow-up DTC patients were collected retrospectively 6 months or more after 131I ablation therapy following total-thyroidectomy or near-total thyroidectomy. The diagnostic standard for DTC metastasis and relapse were based on serum Tg, D-WBS, neck ultrasound and chest CT. Diagnostic 2 by 2 table was employed for calculating the sensitivity, specificity, accuracy of the methods. ResultsThe sensitivity, specificity, accuracy, positive predictive value, negative predictive value of TgIMA and D-WBS parallel experiments were 100.0%, 92.9%, 96.0%, 91.7%, and 100.0% respectively. ConclusionTgIMA combined with D-WBS parallel test in diagnosis of DTC metastasis and recurrence has the highest accuracy.