Diagnostic Efficacy of FNA-Tg in DTC Cervical LN Metastasis and its Impact Factors: A Large Retrospective Study.

Context: Thyroglobulin in needle washout fluid (FNA-Tg) has the advantage of compensating for the low sensitivity of cytological analysis (FNAC) in differentiated thyroid carcinoma (DTC) lymph node (LN) metastasis. However, studies of large data sets to support this view and identify the best cutoff of FNA-Tg are lacking. Objective: Our study aimed to determine the best cutoff of FNA-Tg and explore the impact factors of FNA-Tg. Method: A total of 1106 suspicious LNs from patients treated at West China Hospital from October 2019 to August 2021 were included. Parameters were compared between metastatic and benign LNs, and the best cutoff value of FNA-Tg was identified by ROC curves. The impact factors of FNA-Tg were analyzed. Results: In the nonsurgery group, after correcting for the effect of age and short diameter of LN, FNA-Tg was the independent risk factor for cervical LN metastasis of DTC (odds ratio [OR]: 1.048; 95% CI, 1.032-1.065). In the surgery group, after correcting for the effects of serum thyrotropin, serum Tg, long diameter of LN, and short diameter of LN, FNA-Tg was the independent risk factor for cervical LN metastasis of DTC (OR: 1.019; 95% CI, 1.006-1.033). The best cutoff value of FNA-Tg was 25.17 µg/L, and the area under the receiver operating characteristic curve, sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 0.944, 0.847, 0.978, 0.982, 0.819, and 0.902, respectively. FNA-Tg highly correlated with FNA-TgAb (P< .01; Spearman correlation coefficient = 0.559), but FNA-TgAb positivity did not undermine the diagnostic efficacy of FNA-Tg for DTC LN metastasis. Conclusion: The best cutoff value of FNA-Tg was 25.17 µg/L in diagnosing DTC cervical LN metastasis. FNA-Tg highly correlated with FNA- TgAb, but FNA-TgAb had no influence on the diagnostic efficacy of FNA-Tg. [ABSTRACT FROM AUTHOR]