Endocrine Abstracts

JOINT1014

Background: Thyroid nodules with non-diagnostic or atypia of undetermined significance (AUS) cytology results often require repeat testing, leading to diagnostic delays and uncertainty. CYFRA 21-1, a fragment of cytokeratin-19, has been suggested as a complementary biomarker to improve diagnostic accuracy and predict malignancy in such ambiguous cases. This study aims to evaluate the diagnostic and predictive utility of washout CYFRA 21-1 in thyroid nodules.

Methods: This retrospective study analyzed data from 153 patients with thyroid nodules who underwent fine-needle aspiration cytology (FNAC). Washout CYFRA 21-1 levels were measured from FNAC washout fluid. Diagnostic performance was assessed using receiver operating characteristic (ROC) curve analysis to identify the optimal washout CYFRA 21-1 cutoff value by maximizing the Youden index. Multivariate logistic regression analysis was performed to evaluate the association between washout CYFRA 21-1 levels and thyroid cancer.

Results: The mean washout CYFRA 21-1 level was 53.25 ± 146.14 ng/mL. Of the nodules, 13.73% were thyroid cancer, while 81.70% were benign. Non-diagnostic and follicular neoplasm cases accounted for 1.96% and 2.61%, respectively. Most nodules were classified as K-TIRADS 4 (49.02%) or 5 (21.57%). Washout CYFRA 21-1 levels demonstrated a significant association with malignancy, with levels markedly higher in PTC compared to benign or indeterminate outcomes (P < 0.0001). The optimal cutoff value for washout CYFRA 21-1 was 60.39 ng/mL, achieving a sensitivity of 88.0%, specificity of 94.5%, positive predictive value of 82.8 %, negative predictive value of 93.8%, and accuracy of 90.2% (AUC = 0.833). Multivariate analysis showed that high CYFRA 21-1 levels (≥ 60.39 ng/mL) were strongly associated with malignancy (adjusted OR: 9.257, 95% CI: 13.452–180.356, P < 0.0001).