UNASSIGNED: The 2015 American Thyroid Association (ATA) Guidelines recommend the following size cut-offs based on sonographic appearances for subjecting nodules to fine-needle aspiration (FNA) biopsy: low risk: 15 mm and intermediate risk and high risk: 10 mm.
UNASSIGNED: We conducted a \'real-world\' study evaluating the diagnostic performance of the ATA cut-offs against increased thresholds, in the interest of safely limiting FNAs.
UNASSIGNED: We performed a retrospective analysis of prospectively collected data on 604 nodules which were sonographically risk-stratified as per the ATA Guidelines and subsequently subjected to ultrasound-guided FNA. Nodules were cytologically stratified into \'benign\' (Bethesda class 2) and \'non-benign\' (Bethesda classes 3-6). We obtained the negative predictive value (NPV), accuracy, FNAs that could be spared, missed \'non-benign\' cytologies and missed carcinomas on histology, according to the ATA cut-offs compared to higher cut-offs.
UNASSIGNED: In low-risk nodules, the high performance of NPV (≈91%) is unaffected by increasing the cut-off to 25 mm, and accuracy improves by 39.4%; 46.8% of FNAs could be spared at the expense of few missed B3-B6 cytologies (7.9%) and no missed carcinomas. In intermediate-risk nodules, a 15 mm cut-off increases the NPV by 11.3% and accuracy by 40.7%. The spared FNAs approach 50%, while B3-B6 cytologies are minimal, with no missed carcinomas. In high-risk nodules, low NPV (<35%) and accuracy (<46%) were obtained regardless of cut-off. Moreover, the spared FNAs achieved at higher cut-offs involved numerous missed \'non-benign\' cytologies and carcinomas.
UNASSIGNED: It would be clinically safe to increase the ATA cut-offs for FNA in low-risk nodules to 25 mm and in intermediate-risk nodules to 15 mm.

Several ultrasound (US) risk stratification systems (US-RSSs) have been proposed to stratify the risk of malignancy (ROM) of thyroid nodules. This risk might be overestimated due to selection bias and comparison with the cytological report alone. Our study aimed to compare ROM and diagnostic performance of three guidelines (ATA, AACE/ACE/AME, EUTIRADS) and evaluate the changes in unnecessary biopsy according to the nodule size cutoff for biopsy, using histology as gold standard.
This retrospective observational study included 146 consecutive patients who underwent surgery after US and cytological characterization. We analyzed the effectiveness and accuracy of three US-RSSs.
46.6% of nodules were diagnosed as malignant. Applying US-RSS, the percentage of nodules that should have been analyzed by biopsy was 84.25% with ATA, 69.86% with EUTIRADS and 64.38% with AACE/ACE/AME systems. The ROM was 94.9%, 86.0%, 87.0% for high-risk category, 36.4%, 32.0%, 35.4% for intermediate-risk category and 22.9%, 0.0%, 22.9% for low-risk category by ATA, AACE/ACE/AME and EUTIRADS systems, respectively. EUTIRADS and AACE/ACE/AME systems were more accurate in differentiating malignant from benign cases. ATA score was the more sensitive US-RSS to identify malignant tumors within the high-risk category. About the unnecessary biopsies, in the intermediate-risk category, the application of the size criterion helps to increase specificity in all systems.
The US categorization of low and high-risk thyroid nodules using current US-RSSs helps alone to determine the optimal treatment option. Nodule size remains relevant to recommend biopsy for the intermediate-risk category.

BACKGROUND: Fine needle aspiration (FNA) cytology fails to provide a conclusive diagnosis in a subset of thyroid lesions labeled as \"indeterminate\" (Thy3). In this study, we aimed at ascertaining the prevalence of Thy3 thyroid nodules in a hitherto unreported ethnic group (residents of the United Arab Emirates).
METHODS: We retrospectively examined 688 FNA of the thyroid performed on 584 patients. Samples were reported using the Royal College of Physicians\' (RCP) Thy classification. The results of the FNA were correlated with the final surgical specimens. Ultrasonography (US) risk stratification was calculated using a web-based US risk of malignancy calculator.
RESULTS: Overall sample adequacy was 97%. The indeterminate group Thy3 was found in 7% of the samples. The overall risk of malignancy in the Thy3 category was 20%. This risk was very similar in the 2 subgroups of Thy3 (17% in Thy 3a and 22% in Thy3f). Subdividing the Thy3 group into subgroups becomes less necessary if the US scoring is <24.5% since the negative predictive value, in this case, is 100%. Applying this criterion to our population would have had the potential of reducing the percentage of patients referred to surgery from 61 to 43%.
CONCLUSIONS: Proper risk stratification of Thy3 lesions should be based on the combined risk assessment of clinical, cytological, radiological, and molecular data. Such a pragmatic approach is expected to reduce the percentage of inappropriate referrals to surgery.