Diagnostic value of Thyroglobulin Measurement with Fineneedle Aspiration Biopsy for Lymph Node Metastases in Patients with a History of Differentiated Thyroid Cancer

Purpose: The aim of this study was to evaluate the diagnostic value of FNA-Tg for detecting lymph nodemetastases in patients with a history of differentiated thyroid cancer (DTC). Materials and
Methods: A total of58 patients with DTC diagnosis and evidence of single or multiple suspicious cervical lymph nodes were assessed.All underwent total or near-total thyroidectomy with (35 cases) or without (23 cases) radioiodine (RAI) ablation,followed by thyroid stimulating hormone (TSH) suppression therapy. A total of 68 lymph nodes were examined byultrasound-guided fine needle aspiration (US-FNA) for both cytological examination and FNA-Tg measurement.Serum Tg and anti-thyroglobulin antibody (TgAb) levels were also measured. Diagnostic performance includingsensitivity, specificity, accuracy, positive (PPV) and negative predictive value (NPV) of FNAC and FNA-Tg werecalculated and compared. The Spearman’s rank correlation coefficient was used to estimate the relationshipbetween FNA-Tg and serum TgAb.
Results: The FNA-Tg levels were significantly higher with DTC metastaticlymph nodes (median 927.7 ng/mL, interquartile range 602.9 ng/mL) than non-metastatic lymph nodes (median0.1 ng/mL, interquartile range 0.4 ng/mL) (p<0.01). Considering 1.0 ng/mL as a threshold value for FNA-Tg,the sensitivity, specificity, accuracy, PPV and NPV of FNA-Tg were 95.7%, 95.5%, 95.6%, 97.8% and 91.3%,respectively. The sensitivity and accuracy of the combination of FNAC and FNA-Tg were significantly higherthan that of FNAC alone (p<0.05). The diagnostic performance of FNA-Tg was not significantly different betweencases with or without RAI ablation, and the serum TgAb levels did not interfere with FNA-Tg measurements.
Conclusions: Measurement of FNA-Tg is useful. The combination of FNAC and FNA-Tg is more sensitive andaccurate for detecting lymph node metastases in patients with a history of DTC than FNAC alone. Serum TgAbsappear to be irrelevant for measurement of FNA-Tg.