Comparison of the Diagnostic Performance of ACR TI-RADS and EU-TI-RADS for the Detection of Thyroid Malignancy: A Retrospective Study.

Objective The objective of this study was to compare the diagnostic performance of the American College of Radiology Thyroid Imaging Reporting and Data System (ACR TI-RADS) and the European Thyroid Imaging Reporting and Data System (EU-TI-RADS) in differentiating benign from malignant thyroid nodules using guideline-based fine-needle aspiration recommendation as the test-positive criterion, and to evaluate demographic and sonographic predictors of thyroid malignancy in a real-world clinical cohort. Materials and methods This retrospective diagnostic accuracy study included thyroid nodules assessed by ultrasound followed by ultrasound-guided fine-needle aspiration cytology (FNAC), with histopathology used as the reference standard for surgically excised nodules. Ultrasound images were independently reviewed by three experienced consultant radiologists blinded to cytological and histopathological outcomes, with consensus used for disagreements. The definitive cohort comprised 809 nodules: 652 benign and 157 malignant. Nodules without a definitive outcome, including nonoperated Bethesda III/IV cases, were excluded from the primary analysis. Bethesda I nodules remained excluded because they were nondiagnostic. Diagnostic performance was calculated using 2 × 2 contingency tables, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, likelihood ratios, and diagnostic OR (DOR). Paired comparisons were performed using McNemar testing. Multivariable logistic regression was performed to identify independent predictors of malignancy. Sensitivity analyses were performed by classifying excluded nonoperated Bethesda III/IV nodules as benign and malignant in separate scenarios. Results The definitive cohort comprised 809 nodules, including 652 benign nodules and 157 malignant nodules. ACR TI-RADS correctly identified 135 of 157 malignant nodules (sensitivity 85.99%) and correctly excluded 481 of 652 benign nodules (specificity 73.77%). EU-TI-RADS correctly identified 142 of 157 malignant nodules (sensitivity 90.45%) but correctly excluded only 233 of 652 benign nodules (specificity 35.74%). ACR TI-RADS demonstrated higher PPV (44.12% vs 25.31%), NPV (95.63% vs 93.95%), overall accuracy (76.14% vs 46.35%), and DOR (17.26 vs 5.26). EU-TI-RADS had slightly higher sensitivity than ACR TI-RADS (McNemar p = 0.046), whereas ACR TI-RADS had significantly higher specificity (McNemar p < 0.001). Sensitivity analyses including nonoperated Bethesda III/IV nodules yielded similar results. Multivariable logistic regression identified hypoechogenicity, solid or almost entirely solid composition, and taller-than-wide orientation as independent predictors of malignancy, while irregular or lobulated margins and microcalcifications showed quasi-complete separation because of their strong association with malignant nodules. Conclusions Both systems demonstrated high sensitivity and high NPV. In this primary healthcare cohort, ACR TI-RADS provided substantially higher specificity and overall accuracy, suggesting greater potential to reduce unnecessary FNAC, whereas EU-TI-RADS offered marginally higher sensitivity. Hypoechogenicity, solid or almost entirely solid composition, and taller-than-wide orientation were independent predictors of malignancy. Irregular or lobulated margins and microcalcifications were also strongly associated with malignancy but showed quasi-complete separation.