Diagnostic Value of Applying ACR-TIRADS on Thyroid Nodule Biopsies at a Tertiary Care Centre in the United Arab Emirates: A Prospective Observational Study

Introduction: Incidental thyroid nodules are commonly encountered in clinical practice, and only a minority of these are malignant. Suspicious nodules on ultrasound are subjected to Fine Needle Aspiration Biopsy (FNAB) to rule out malignancy and determine appropriate management. In the United Arab Emirates, medical professionals from various countries practice, and there are no well-established local best practice guidelines for thyroid nodule biopsies. Aim: To determine the percentage of thyroid nodules in which FNAB would be considered unnecessary by applying the American College of Radiology (ACR)-Thyroid Imaging Reporting and Data System (TIRADS) 2017 guidelines.Materials and Methods: A prospective observational study was conducted in the Radiology Department of Belhoul Speciality Hospital, Dubai, United Arabs Emirates from January 2018 to December 2019. A total of 142 thyroid nodules were studied, and FNABs were performed. Two experienced radiologists assigned ACR-TIRADS categories to the nodules. The nodules were divided into groups: Fine-Needle Aspiration (FNA) indicated and FNA not indicated. Surgically resected nodules underwent histopathological examination, and benign or malignant categorisation was based on histopathological findings. Cases with Bethesda II cytology were considered benign, Bethesda V and VI were considered malignant, and 35 cases with Bethesda I, III, or IV cytology were excluded from the study. The final study cohort included 107 nodules with available final reference standard diagnoses. Data were analysed using International Business Machine Statistical Package for Social Sciences (IBM SPSS) Statistics 26.0, and sensitivity, specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV), and Diagnostic Odds Ratio (DOR) {each with 95% Confidence Interval (CI)} were calculated.Results: Out of the 107 nodules included in the study, 15 (14%) were malignant, and 92 (86%) were benign. Applying ACR-TIRADS, biopsy was not indicated in 54 out of 107 patients, resulting in an "unnecessary" biopsy rate of 50.5%. Only two out of the 15 malignant cases were assigned to the FNAC not indicated group due to their subcentimetre size. Therefore, the sensitivity, NPV, and false negative rate of these criteria were 86.7%, 96.3%, and 3.7%, respectively. Conclusion: The ACR-TIRADS guidelines are highly reliable, and if strictly followed, almost half of thyroid nodule biopsies can be safely avoided. However, since ACR-TIRADS does not recommend FNA for subcentimetre thyroid nodules, a few small malignancies may experience delayed diagnosis.