Abstract
<title>Abstract</title> <p> <bold>Objective:</bold> Fine-needle aspiration thyroglobulin (FNA-TG) testing can significantly improve the detection of lymph node metastasis (LNM) in thyroid cancer (TC). However, there is currently no standardized testing protocol for FNA-TG, and results across different studies show significant heterogeneity. Therefore, this study investigated the impact of different eluents on serum thyroglobulin (STG) measurement results in actual clinical practice, with the aim of identifying a suitable FNA eluents and establishing standardized sample processing and testing procedures for FNA-TG. <bold>Methods:</bold> Thirty serum thyroglobulin (STG) samples were selected (10 each for high, medium, and low levels; all samples were negative for Thyroglobulin Antibody (TGAb) were all negative). Using the Roche Cobas e801 chemiluminescence assay, we compared the accuracy and stability (at 0, 1, 3, and 14 days) of four eluents—the original Roche diluent, saline, distilled water, and liquid-based cytology preservation solution—after dilution at a 1:9 ratio to determine the most suitable eluents for TG.A total of 26 clinical specimens from patients with suspected thyroid cancer or suspected cervical lymph node metastasis following thyroid surgery were enrolled. Testing was conducted according to the standardized FNA-TG testing protocol. Saline and the Roche diluent were used as eluents for comparison. FNA-TG test results were compared with those of fine-needle aspiration cytology (FNAC), and the clinical concordance rate was calculated. <bold>Results:</bold> Saline and Roche diluent can both be used as eluents for FNA-TG testing, and demonstrate good stability within 14 days ( <italic>all p</italic> > 0.05). Liquid-based cytology preservation solution and distilled water are not suitable as eluents for TG, as they significantly reduce detection accuracy and exhibit poor stability ( <italic>p</italic> < 0.01). In clinical samples, saline and Roche diluent were compared as eluent for detection, showing no significant fixation bias or proportionality bias, with good consistency. The concordance rate between results obtained with eluent and pathological results was 96.1% (25/26), with only one false-positive result caused by interference from residual thyroid tissue. After implementation of a standardized testing process, FNA-TG demonstrates a high concordance rate with clinical diagnoses and is suitable for routine clinical use. <bold>Conclusion:</bold> Saline solution is the most reliable eluents for FNA-TG, and when operated according to a standardized protocol, it is clinically applicable. </p>