Endocrine Abstracts

Introduction: Fine needle aspiration (FNA) for thyroglobulin (Tg) measurement (FNA-Tg) and for cytology (FNAC) are recommended for the evaluation of cervical lymph nodes (LN) suspected as differentiated thyroid carcinoma (DTC) metastases. LN proven to represent a metastasis of thyroid origin, change the operation plan, both prior to surgery and while encountering suspicious LN during surgery.

Aim: To assess the diagnostic accuracy of a novel point-of-care assay for Tg (POC-Tg) (PCT Patent Application No. PCT/IL2022/050067), able to detect qualitatively, within minutes, Tg in the needle washout of a suspicious LN.

Methods: Limit of detection for Tg was set at a concentration of 5 ng/ml following needle dilution with 1 mL of 0.9% saline. The POC-Tg was assessed in the FNA clinic when a LN suspected as DTC metastasis was biopsied; and in the operating room (OR) when suspicious LN was found during thyroid surgery. Each LN was evaluated using both the formal method (FNA clinic- FNAC and FNA-Tg; OR- ‘frozen-section’), and the POC-Tg. Clinical decisions were made according to the formal evaluation only. The POC-Tg performance was analyzed retrospectively.

Results: FNA clinic: 22 sonographically suspicious LN were tested. Eleven were found to be positive in both our POC-Tg and the formal Tg immunoassay, with final histology reporting metastatic DTC. Ten LN were negative in both our POC-Tg and the standard Tg immunoassay, all with benign cytology. One metastatic LN, as was proven by final histology, was negative in our POC-Tg but showed low detectable Tg in the standard immunoassay.

OR: Four LNs were positive and seven negative in both our POC-Tg, and the ‘frozen-section’ results.

Conclusion: The diagnostic accuracy of the POC-Tg for LN metastases of DTC origin exceeded 95%, thus might change diagnostic and treatment algorithms.