Objectives: The prevalence of thyroid nodules in adults, detected by ultrasound (US), is reported as high as 68%. US-guided fine-needle aspiration biopsy (FNAB) is the test of choice used to determine the nature of the nodules. However, not more than 15% are found to be malignant. Reducing the number of unnecessary FNAB while identifying clinically significant malignant nodules is imperative. There are several guidelines suggested for risk stratification of thyroid nodules by US. The aim of our study was to validate and compare Thyroid Imaging Reporting and Data System (TIRADS) American College of Radiology (ACR) and American Thyroid Association (ATA) risk stratification, specifically pertaining to reduction of unnecessary biopsies. Material and Methods: The study included 281 nodules in 245 patients who underwent FNAB between May 2018 and June 2019. Statistical analysis was performed only on 235 nodules that according to the TIRADS ACR and/ or ATA guidelines were eligible for FNAB. Data collected included nodule characteristics with corresponding TIRADS and ATA grading and cytological results using Bethesda scoring. Results: An agreement was found between the two criteria methods in 58.2% (137/235) of the cases. In 35.3% (83/235), ATA recommended FNAB while TIRADS did not. The specificity for ATA criteria was 7% (15/221) and for TIRADS was 37% (81/221). The sensitivity was 100% (14/14) for ATA and 86% (12/14) for TIRADS. Conclusion: Application of ACR TIRADS criteria can reduce the number of US-guided FNAB performed on benign nodules compared to ATA criteria, by 35%, with a cost of only two missed carcinomas that remained on further follow-up.

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