Correlation between the Thyroid Image and Reporting Data System (TIRADS) and the Bethesda System for Reporting the Thyroid Cytopathology in Patients with Thyroid Nodules

Abstract Background : The thyroid imaging and reporting data system (TIRADS) has been routinely used to report thyroid nodules since its introduction in 2017. Similarly, the Bethesda system is a well-validated method used to report the cytopathology of thyroid lesions for over a decade. The aim of this study was to investigate the correlations between these two systems. Methods : This retrospective cohort study comprised patients who underwent ultrasound assessments of the thyroid gland followed by fine needle aspiration cytology (FNAC) of the thyroid nodules at a teaching hospital. The variables were categorised into ultrasound and cytological findings, and the outcomes measured from the two systems (validity of the system and risk of malignancy in each group of thyroid nodules) were correlated. Spearman’s correlation was used to determine the correlation, and the Kappa test was used to determine the agreement between the systems. Results : A total of 295 patients who fulfilled the inclusion criteria were identified during the study period. Females represented 82.7% of the study population, and the majority of the patients presented with multiple thyroid nodules (74.2%) and bilateral diseases (60.7%). The number of patients with TIRADS 3 and 4 nodules was 102 and 132, respectively, whereas the highest number of patients (n = 231) presented with the Bethesda II subcategory. Only 31.5% of the patients underwent thyroidectomy, and 18.3% had a final histological diagnosis of thyroid malignancy. The Spearman’s correlation value (ρ) between TIRADS and Bethesda was 0.464 (p < 0.001), and the linear-weighted kappa was 0.203 (95% confidence interval [CI], 0.153–0.253), indicating a good correlation between the two systems. Both systems showed good diagnostic accuracy (area under the curve [AUC], 85.8% and 85.6%, respectively). The malignancy risks for TIRADS 2, 3, 4 and 5 were 0%, 2.9%, 18.2% and 93.1%, respectively. Conclusions : Good correlations were observed between the TIRADS and Bethesda systems. Thus, they can be used to predict the cytological results of FNAC, which will aid in achieving more accurate decisions for both biopsy and surgical interventions while managing the thyroid nodule.