Cyto-Radiological Correlation of Nodular Thyroid Lesions Using the Bethesda and American College of Radiology-Thyroid Imaging Reporting and Data System (ACR TI-RADS) Classification Systems: A Cross-Sectional Study.

BACKGROUND: Thyroid nodules are a common clinical finding, and accurate preoperative risk stratification is essential to avoid unnecessary surgery while ensuring timely detection of malignancy. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) and the American College of Radiology Thyroid Imaging Reporting and Data System (ACR TI-RADS) are widely used but are frequently applied in isolation. We evaluated their correlation, agreement, and combined diagnostic utility in nodular thyroid disease. METHODS: This hospital-based cross-sectional study enrolled 80 consecutive patients with nodular thyroid lesions at a tertiary care centre over 18 months. Each nodule underwent ultrasonographic ACR TI-RADS categorisation and fine-needle aspiration cytology (FNAC) reported per TBSRTC (2023 edition); serum triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH) were measured. Agreement (Cohen's kappa), diagnostic accuracy, receiver operating characteristic (ROC) analysis, and multivariable logistic regression were performed. RESULTS: The mean age was 46 ± 16.4 years with marked female predominance (86.25%). Bethesda II (87.5%) and TI-RADS 2 (57.5%) were the commonest categories. The risk of malignancy rose progressively across TI-RADS categories (0% in TR1-TR2 to 50% in TR5). Overall cyto-radiological concordance was 85% (κ = 0.42, moderate). For predicting malignancy, TI-RADS showed sensitivity 77.8%, specificity 90.3%, negative predictive value (NPV) 93.3%, and accuracy 87.5% (area under the curve (AUC) 0.91), while Bethesda cytology showed specificity 87.3% and NPV 95.4%. Bethesda category (odds ratio (OR) 3.8), TI-RADS category (OR 2.6), and elevated serum T3 (OR 1.9) were independent predictors of malignancy. Concordant high-risk categorisation was uniformly malignant. CONCLUSION: ACR TI-RADS and the Bethesda system are complementary. Their integrated application improves malignancy risk stratification, reliably excludes malignancy in low-risk nodules, and may reduce unnecessary diagnostic interventions.