Diagnostic value of thyroglobulin measurement in fine-needle aspiration biopsy for detecting lymph nodes metastasis in patients with papillary thyroid cancer

Objective To investigate the diagnostic value of thyroglobulin measurement in fine-needle aspiration biopsy(FNA-Tg).Methods This study included 63 patients with thyroid cancer or with enlarged lymph nodes during the follow-up from Aug.2010 to Jun.2012.Ultrasound-guided fine-needle aspiration was done in the 63 patients with 79 suspicious enlarged lymph nodes.Then thyroglobulin(Tg) in FNA washout fluid and serum Tg were assayed with electrochemiluminescenceimmunoassay(ECLIA).Diagnostic sensitivity,specificity and area under the ROC curve were evaluated according to 5 predetermined threshold levels:FNA-Tg/serum-Tg ＞ 1,mean + 2SD of node-negative patients,10 ng/ml,optimal operating point of ROC curve and 1000 ng/ml.Results The sensitivity value was 90.70％,90.70％,95.35％,90.70％ and 65.12％ respectively on the 5 threshold level,significantly lower than those on the threshold level of 1000 ng/ml(P ＜0.05).The specificity value was 97.22％,91.67％,72.22％,97.22％ and 100％ (P ＞0.05) on those threshold levels,significantly lower than those on the threshold level of 10 ng/ml (P ＜0.05).The area under the ROC curve was 0.940,0.912,0.838,0.940 and 0.826 respectively.There was no statistical difference(P ＞0.05).Conclusion Selecting FNA-Tg/serum-Tg ＞ 1 as a positive threshold value can be a secondary diagnosis of lymph nodes metastasis in patients with papillary thyroid cancer. Key words: Fine-needle aspiration; Thyroglobulin; Lymphatic metastasis; Papillary thyroid cancer