Background and purpose: It was controversial that value of the first pre-ablation stimulated thyroglobulin (sTg) in the diagnosis of recurrence or metastasis of differentiated thyroid carcinoma (DTC)

due to the influence of many factors such as residual thyroid. In this study

we investigated the significance of the first pre-ablation sTg in predicting neck and distant meta

stasis in postoperative patients with DTC. Methods: The study included 106 patients with DTC who had undergone total thyroidectomy and lymphadenectomy. The pre-ablation sTg of 106 patients was measured one day before the first

131

I ablation therapy

and the patients underwent

131

I whole-body imaging and SPECT/CT fusion imaging 5-7 days after

131

I ablation therapy. Patients were divided into 3 groups as M0 group

M1 group and M2 group according to the presence and absence of metastases

respectively. The sTg values between groups were compared by Mann-Whitney rank-sum test. The ROC curves and diagnostic critical point (DCP) were analyzed to evaluate the predictive value of sTg. Results: The pre-ablation sTg of M1 group and M2 group were significantly higher than that of M0 group (U=143.00

P0.01; U=60.00

P0.01). Areas under the ROC curve for sTg were 0.872 and 0.964

respectively. The cut-off values of DCP of sTg were 23.95 ng/mL with a sensitivity of 68.42%

specificity of 100%

accuracy of 92.31%

and 20.93 ng/mL with a sensitivity of 85.71%

specificity of 100%

accuracy of 95.40%

respectively. Conclusion: The pre-ablation sTg value may be a useful diagnostic marker for predicting metastasis before the first

131

I ablation therapy

especially for the prediction of distant metastasis.