Association between American College of Radiology Thyroid Imaging Reporting and Data System and Bethesda Scoring System in Assessment of Thyroid Nodule: A Prospective Cross-sectional Study

Introduction: In view of increased detection of incidental thyroid nodules on ultrasonography, there is a need for standardising the reporting system of thyroid nodules for better patient management. Aim: To assess concordance between two classification systems of thyroid nodules: American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TIRADS) 2017 criteria on sonography and Bethesda categories on cytology. Materials and Methods: A prospective, cross-sectional validation study was conducted in Department of Radiology in collaboration with the Department of Pathology at a tertiary care hospital in Dakshina Kannada district, Karnataka, India, over a period of 12 months between October 2017 to September 2018. A total of 175 thyroid nodules detected on Ultrasonography (USG) were categorised based on ACR TIRADS 2017 criteria. Ultrasound guided Fine Needle Aspiration Cytology (FNAC) was performed on the nodules and were scored on the basis of Bethesda categories. Nodules were categorized into benign and malignant under TIRADS and Bethesda and their concordance was assessed. Sensitivity, specificity, positive and negative predictive value were assessed. Pearsons Chi-square test statistical method and kappa values were used in analysis. Results: Solid composition, hypoechoic echotexture, taller than wide shape, irregular margin and microcalcification descriptors of ACR TIRADS 2017 system were features more in favour of a malignant nodule. With FNAC as gold standard, TIRADS had a sensitivity, specificity, positive and negative predictive value and diagnostic accuracy of 91.7 %, 86.3%, 63.5%, 97.6% and 87.4% respectively (p-value <0.001). Conclusion: The stratification of risk among thyroid nodules as benign or malignant using ACR TIRADS 2017 criteria yielded good result in our study. With careful examination of nodules, TIRADS can be used to select appropriate nodules for further evaluation with cytology.