Concordance between BETHESDA Cytology Classification and ACR-TIRADS Ultrasound Classification in the Evaluation of Thyroid Nodules at Tikur Anbesa Specialised Hospital, Addis Ababa, Ethiopia: A Prospective Study from April 2023 to October 2023

Background and objective: The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) is a widely used systemof reporting currently helping in the management of thyroid nodules, which are common and mostly benign. The AmericanCollege of Radiology Thyroid Imaging Reporting and Data System (ACR-TIRADS) is also a widely used classification systemthat has helped in screening for nodules requiring subsequent fine needle aspiration cytology, but the correlation between thetwo systems has not been established in our setup. This study aims to determine the level of concordance between the cytologycategory based on TBSRTC 2017 and the ultrasound TIRADS category based on ACR-TIRADS 2017.Methodology: It was a prospective cross-sectional study over 6 months that included 92 patients with thyroid nodules. In allcases, the thyroid ultrasound and cytology findings were reported based on ACR-TIRADS 2017 and TBSRTC 2017, respectively.The level of agreement between ACR-TIRADS and TBSRTC systems was expressed as a kappa value.Results: Study subjects were mostly women (84%), with an average age of 47.60 years. The highest frequency in the Bethesdasystem was seen in category II (54/92) and category V (17/92). In contrast, the highest frequency in TIRADS was in category4 (45/92) and category 3 (21/92). Maximum concordance was found among the categories 2-II and 5-V of the classificationsystems. The overall observed agreement was 65.2% with a linear weighted kappa of 0.343 (95% CI: 0.213-0.472). A higherweighted kappa value was seen in males, nodules ≥4 cm, individuals aged <50 years and in those whose fine needle aspirationwas done with freehand.Conclusion: The study revealed a fair concordance between cytologic diagnosis based on the TBSRTC and ultrasound diagnosisbased on the ACR-TIRADS, with the highest concordance seen in the two ends of the classification categories (TIRADS5-Bethesda V and TIRADS 2-Bethesda II). Careful interpretation of the ultrasound findings and cytologic specimens allows thetreating physicians to decide which nodules need surgery and follow-up so that there will be no unnecessary surgical proceduresand complications. There should be an institutional monitoring system for nodules with discordant Bethesda and TIRADScategories, especially for those with extreme categories that are produced.