The influence of thyroid status, serum Tg , TSH , and TgAb on FNA‐Tg in cervical metastatic lymph nodes of papillary thyroid carcinoma

Objective Papillary thyroid carcinoma is treated in China mostly with surgery, including total ablation, lobectomy, and lobe and isthmus resection. Therefore, whether thyroid status affects the FNA‐Tg cutoff value in the diagnosis of cervical lymph node metastasis deserves our attention. In addition, we investigated the influence of serum Tg, TSH, and TgAb on the accuracy of using FNA‐Tg for diagnosis. Methods Our retrospective analysis included 189 suspected cervical lymph nodes, and we determined whether the cutoff value of FNA‐Tg was affected by thyroid status, sTg, sTSH, and sTgAb. Results In thyroid present cases, the optimal cutoff value of FNA‐Tg was 2.3 ng/ml (sensitivity 96.2%, specificity 100%), and in the thyroid absent cases, the optimal cutoff value of FNA‐Tg was 0.7 ng/ml (sensitivity 97.6%, specificity 96.0%). Although serum Tg, TSH, and TgAb were weakly correlated with FNA‐Tg values, they did not affect the diagnostic performance of the optimal cutoff value of FNA‐Tg according to thyroid status. Conclusions The optimal cutoff value of FNA‐Tg should be selected according to the thyroid status (2.3 ng/ml for thyroid present cases and 0.7 ng/ml for thyroid absent cases) to ensure the efficient diagnosis of cervical metastatic lymph nodes of papillary thyroid carcinoma. It was determined that sTg, sTSH, and sTg‐Ab cannot influence the diagnostic performance of FNA‐Tg. The combination method of FNA‐Tg and FNAC is the most optimal choice for the diagnosis of lymph nodes metastasis.