ObjectiveAntithyroglobulin antibody (TgAb) is a potential tumour marker for detecting differentiated thyroid cancer (DTC) recurrence, but insufficient data have supported its clinical applications. Our study aimed to describe the changing trend of TgAb after surgery and identify the relationship between this trend and clinical outcomes.Patients and MethodsWe reviewed the electronic records of 1,686 DTC patients who had undergone total thyroidectomy (TT) and radioactive iodine (131I) therapy at West China Hospital of Sichuan University from January 2015 to December 2017. Finally, 289 preoperative TgAb-positive DTC patients were included and divided into four subgroups depending on the clinical outcome: Group A (tumour free), Group B (uncertain), Group C (incomplete biochemical response), and Group D (structural disease). The patient demographics, tumour characteristics, operations, pathology reports, and all serological biomarkers were reviewed and compared, and the prognostic efficacy of TgAb was evaluated.ResultsAmong all 1,686 patients, 393 (23.65%) were TgAb positive (>40 IU/ml) preoperatively. The TgAb level in Group A decreased significantly after surgery and 131I therapy and stabilised at a low level after 1–2 years of 131I therapy. However, in the other three groups, the decrease in TgAb was not significant after treatment. Conversely, TgAb declined slowly and remained stable or increased. The variations in TgAb relative to the preoperative level of Group A were significantly larger than those of Groups B, C, and D at most time points of follow-up (p < 0.001). By receiver operating characteristic (ROC) analyses, the variations of TgAb > −77.9% at 6 months after 131I therapy (area under the curve (AUC) = 0.862; p < 0.001) and TgAb > −88.6% at 2 years after 131I therapy (AUC = 0.901; p < 0.001) had good prognostic efficacy in tumour-free survival. When the variation in TgAb > −88.6% at 2 years after 131I therapy was incorporated as a variable in the American Thyroid Association (ATA) categories, both intermediate- and high-risk patients also had a significantly increased chance of being tumour free (from 75.68% to 93.88% and 42.0% to 82.61%, respectively).ConclusionsFor preoperative TgAb-positive DTC patients, variations in TgAb > −77.9% at 6 months after 131I therapy and TgAb > −88.6% at 2 years after 131I therapy had good prognostic efficacy. Their incorporation as variables in the ATA risk stratification system could more accurately predict disease-free survival.

Background 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 datasets to support this view and identify the best cut-off of FNA-Tg are lacking. 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 cut-off value of FNA-Tg was identified by ROC curves. The impact factors of FNA-Tg were analysed. Results In Group of Non-surgery, 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 (OR: 1.048, 95%CI: 1.032-1.065). In Group of Surgery, after correcting for the effects of s-TSH, s-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 cut-off value of FNA-Tg was 25.17 ug/L, and the AUC, sensitivity, specificity, PPV, NPV, 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<0.01, 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 cut-off value of FNA-Tg was 25.17 ug/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.

Background Calcitonin (Ctn) is a tumor marker of medullary thyroid carcinoma (MTC). However, serum Ctn cutoff values for MTC diagnosis are still under discussion. This study aimed to identify the cutoff values of Ctn and explore the relationship between two tumor markers (Ctn and carcinoembryonic antigen (CEA)) and disease burden. Methods This was a retrospective study conducted in West China Hospital of Sichuan University. We included 61 MTC patients and 235 non-MTC patients with nonspecific elevation of Ctn (> 9.52 pg/mL for males and > 6.40 pg/mL for females) and collected patients’ demographic information, essential serological indicators, cervical ultrasound and pathological reports. Results Unlike MTC, papillary thyroid carcinoma (40.85%), uremia (18.73%), chronic renal disease (10.21%) and inflammation (8.94%) commonly occurred with hypercalcitoninemia. The Ctn cutoff values were 38.24 pg/mL for males and 26.00 pg/mL for females. The Ctn level was found to be positively related to the largest tumor diameter (r = 0.702). Serum Ctn levels were significantly higher in patients with lymph node metastasis than in those without (P < 0.05), but CEA levels did not differ (P > 0.05). Conclusion The best Ctn cutoff values for Chinese people to discriminate MTC from other hypercalcitoninemia conditions are 38.24 pg/mL for males and 26.00 pg/mL for females.