Comparison of the diagnostic performance of the modified Korean Thyroid Imaging Reporting and Data System for thyroid malignancy with three international guidelines

Purpose: This study compared the diagnostic performance of the modified Korean Thyroid Imaging Reporting and Data System (K-TIRADS) for thyroid malignancy with three international guidelines. Methods: From June to September 2015, 5,708 thyroid nodules (>= 1.0 cm) in 5,081 consecutive patients who underwent thyroid ultrasound (US) at 26 institutions were evaluated. The US features of the thyroid nodules were retrospectively reviewed and classified according to all four guidelines. In the modified K-TIRADS, the biopsy size threshold was changed to 2.0 cm for K-TIRADS 3 and 1.0 or 1.5 cm for K-TIRADS 4 (K-TIRADS(1.0cm) and K-TIRADS(1.5cm), respectively). We compared the diagnostic performance and unnecessary fine-needle aspiration biopsy (FNAB) rates for thyroid malignancy between the modified K-TIRADS and three international guidelines. Results: Of the 5,708 thyroid nodules, 4,597 (80.5%) were benign and 1,111 (19.5%) were malignant. The overall sensitivity was highest for the modified K-TIRADS(1.0cm) (91.0%), followed by the European (EU)-TIRADS (84.6%), American Association of Clinical Endocrinologists/American College of Endocrinology/Associazione Medici Endocrinologi (AACE/ACE/AME) (80.5%), American College of Radiology (ACR)-TIRADS (76.1%), and modified K-TIRADS(1.5cm) (76.1%). For large nodules (>2.0 cm), the sensitivity increased to 98.0% in both the modified K-TIRADS(1.0cm) and K-TIRADS(1.5cm). For small nodules (<= 2.0 cm), the unnecessary FNAB rate was lowest with the modified K-TIRADS(1.5cm) (17.6%), followed by the ACR-TIRADS (18.6%), AACE/ACE/AME (19.3%), EU-TIRADS (28.1%), and modified K-TIRADS(1.0cm) (31.2%). Conclusion: The modified K-TIRADS(1.5cm) can reduce the unnecessary FNAB rate for small nodules (1.0-2.0 cm), while maintaining high sensitivity for detecting malignancies >2.0 cm.