Point Of Care Thyroglobulin Lateral Flow Immunoassay for Rapid Detection of Differentiated Thyroid Carcinoma Metastasis to Cervical Lymph Nodes

Metastatic cervical lymph nodes (LN) are detected in 20-30% of patients with differentiated thyroid cancer (DTC). Current guidelines recommend that once a cervical LN is suspected to be DTC metastasis during a neck ultrasound (US) procedure, it should be investigated via a fine needle aspiration (FNA) biopsy for cytological evaluation and saline washout of the needle for thyroglobulin (Tg) measurement (FNA-Tg). Since Tg is a protein produced exclusively by thyroid follicular cells, a positive FNA-Tg result establishes the diagnosis of metastatic DTC irrespective of cytology. The conventional, immunoassay-based, FNA-Tg washout requires a laboratory and skilled personnel. We developed a semi-quantitative, lateral flow-based method which was shown to detect at the point-of-care (POC), within 10 minutes, positive Tg samples in needle washouts of a suspicious LN at the site of FNA biopsy. In the pre-clinical phase, the POC-Tg limit of detection was determined to be at a concentration equal to 5 ng/mL, after a 1 mL dilution with normal saline. Our prototype was optimized by evaluating different components: types of membranes, pads, antibodies, and gold conjugates. We evaluated our POC-Tg kits on thirty clinical samples: 16 were found positive while the other 14 were seen as negative. All the negative and positive results were further validated by the attending clinical labs, resulting in 100% compatibility compared to the standard procedure. The proof-of-value of our POC-Tg test lies in its ability to significantly reduce the time to results, thus enhancing clinical decision-making, and saving time and valuable resources.