Lowered cutoff of lymph node fine-needle aspiration thyroglobulin in thyroid cancer patients with serum anti-thyroglobulin antibody

Abstract

Objective: Fine needle aspiration cytology (FNAC) and measurement of thyroglobulin (Tg) in needle washout (FNA-Tg) are recommended for the diagnosis of metastatic or recurrent lymph nodes (LNs) in differentiated thyroid cancer (DTC). However, the effect of serum Tg antibody (TgAb) on FNA-Tg levels still remains unclear in the preoperative setting. We analyze the interference of serum TgAb on FNA-Tg levels as proof of concept in the diagnostic advantage of serum TgAb combined with FNA-Tg. Subjects and methods: A total of 370 suspicious cervical LNs from 273 patients with DTC were included. The primary tumor was confirmed as DTC on preoperative pathology in all patients. We performed FNA-Tg measurement and FNAC on suspicious LNs and evaluated the diagnostic performance of FNAC and FNA-Tg according to TgAb status. Final diagnoses were confirmed by histological examination of excised specimens or by follow-up ultrasonography for at least 6 months. Results: Data from 273 subjects with suspicious 370 LNs were evaluated. Fifty-five LNs (14.9%) were from TgAbC positive serum TgAb (TgAbC) patients. Serum Tg and FNA-Tg levels were significantly lower in patients with TgAbC than in those with TgAb-negative (TgAbK). Final pathology confirmed 109 LNs (29.5%) asmalignant. Diagnostic performance of FNA-Tg at the same cutoff level was lower in the TgAbC than TgAbK group. FNA-Tg cutoff levels determined by ROC curve were lower in the TgAbC group. Conclusion: The results suggested that the cutoff value of FNA-Tg should be lowered in suspicious LN before thyroidectomy in thyroid cancer patients with TgAb.

Measurement of thyroglobulin, calcitonin, and PTH in FNA washout fluids

“…In particular, Baskin [80] recorded no interference, and then similarly, Boi et al [31] demonstrated that, although TgAb positivity could determine a slightly underestimation of FNA-Tg concentrations, no false positive cases were found in their data. Meanwhile, some studies described lower FNA-Tg concentrations in washout fluids containing TgAb [18,76,81,82], suggesting that this finding might be due to blood contamination or active intra-nodal TgAb synthesis [83]. Interestingly, in his study, Spencer [84] showed that any detectable level of TgAb, although lower than the cutoff of positivity, has the potential to interfere with Tg measurement relative to its level.…”

Impact of Serum TSH and Anti-Thyroglobulin Antibody Levels on Lymph Node Fine-Needle Aspiration Thyroglobulin Measurements in Differentiated Thyroid Cancer Patients

“…Nevertheless, there is still some debate on defining the best cutoffs according to the clinical situation, with higher cutoffs suggested in non-thyroidectomized patients [16]. Moreover, one study suggests that positive serum anti-thyroglobulin antibodies (TgAb) lowered FNA-Tg levels and influenced the diagnostic accuracy of FNA-Tg in suspicious LNs of preoperative patients [17, 18], while others raise the possibility that suppressed thyrotropin (TSH) resulted in false-negative FNA-Tg in malignant cases [16]. Lack of method standardization makes interpretation difficult [19, 20].…”

Clinical impact of thyroglobulin (Tg) and Tg autoantibody (TgAb) measurements in needle washouts of neck lymph node biopsies in the management of patients with papillary thyroid carcinoma

“…(31) also identified a higher percentage of LNs with low levels of Tg-FNAB in sTgAb+ patients than sTgAb-patients. These authors concluded that the presence of sTgAb interfered with the Tg-FNAB levels; however, these researchers did not measure TgAb in FNAB washout fluid samples (27,31).…”