Ultrasound parameters affecting the diagnostic accuracy of ultrasound-guided fine-needle aspiration for thyroid nodules.

Ultrasound-guided fine-needle aspiration (US-FNA) is central to the evaluation of thyroid nodules. However, specific ultrasonographic parameters may influence sampling adequacy and cytologic classification. This study assessed the diagnostic accuracy of shear-wave elastography (SWE)-guided US-FNA and identified ultrasound features associated with misclassification. This retrospective study enrolled adults undergoing US-FNA between January 2023 and December 2024 according to American Thyroid Association indications. Conventional ultrasound and SWE were used to localize the stiffest intranodular region for targeted aspiration. Surgical histopathology served as the reference standard. Variables included demographics, Hashimoto's thyroiditis, nodule size, calcification, cystic proportion, carotid pulsation, and nodule-to-carotid distance. Agreement was quantified by Kappa (κ). Factors associated with diagnostic accuracy were examined using univariate and multivariable logistic regression, reported as odds ratios (ORs) with 95% confidence intervals (CIs). A total of 186 patients with 200 nodules were analyzed: 80 malignant (predominantly papillary thyroid carcinoma) and 120 benign. SWE-guided US-FNA yielded sensitivity 92.5%, specificity 88.3%, accuracy 90.0%, positive predictive value 84.1%, negative predictive value 94.6%, and κ = 0.81 (P < .001). On multivariable analysis, nodule diameter < 10 mm (OR: 2.84, 95% CI: 1.17-6.90), intranodular calcification (OR: 2.12, 95% CI: 1.01-4.47), and cystic component > 50% (OR: 3.36, 95% CI: 1.18-9.56) independently reduced diagnostic accuracy. SWE-guided US-FNA demonstrates high concordance with histopathology. Small size, calcification, and cyst-predominant composition are independent risk contexts for misclassification and should inform pre-procedural planning, target selection, and adequacy safeguards.