Abstract
Simple SummaryAlthough ultrasound-based risk stratification systems (RSSs) including Thyroid Imaging, Reporting and Data Systems (TIRADSs) may play an important role in triaging nodules with nondiagnostic/unsatisfactory cytology, no previous studies have compared ultrasound-based RSSs for these nodules. In this retrospective, longitudinal, real-world study in Korea including 1143 thyroid aspirations with nondiagnostic/unsatisfactory results from 1125 patients, further diagnostic evaluations, including repeat fine-needle aspiration, were conducted more commonly as the categories of ultrasound-based RSSs increased. The American Thyroid Association (ATA) guidelines, Korean (K)-TIRADS, and American College of Radiology (ACR) TIRADS were more competent in predicting malignancy from nondiagnostic/unsatisfactory nodules. The EU-TIRADS, although it was also helpful, demonstrated less effective diagnostic performance in predicting malignancy for nondiagnostic/unsatisfactory nodules in Korea, where iodine intake is more than adequate. These findings have implications for developing and verifying universal guidelines for the ultrasound-based stratification of thyroid nodules and applying these guidelines to nondiagnostic/unsatisfactory nodules.We compared American Thyroid Association (ATA) guidelines, Korean (K)-Thyroid Imaging, Reporting and Data Systems (TIRADS), EU-TIRADS, and American College of Radiology (ACR) TIRADS in diagnosing malignancy for thyroid nodules with nondiagnostic/unsatisfactory cytology. Among 1143 nondiagnostic/unsatisfactory aspirations from April 2011 to March 2016, malignancy was detected in 39 of 89 excised nodules. The minimum malignancy rate was 7.82% in EU-TIRADS 5 and 1.87–3.00% in EU-TIRADS 3–4. In the other systems, the minimum malignancy rate was 14.29–16.19% in category 5 and ≤3% in the remaining categories. Although the EU-TIRADS category ≥ 5 exhibited the highest positive likelihood ratio (LR) of only 2.214, category ≥ 5 in the other systems yielded the highest positive LR of >5. Receiver operating characteristic (ROC) curves of all systems to predict malignancy were located statistically above the diagonal nondiscrimination line (P for ROC curve: EU-TIRADS, 0.0022; all others, 0.0001). The areas under the ROC curve (AUCs) were not significantly different among the four systems. The ATA guidelines, K-TIRADS, and ACR TIRADS may be useful to guide management for nondiagnostic/unsatisfactory nodules. The EU-TIRADS, although also useful, exhibited inferior performance in predicting malignancy for nondiagnostic/unsatisfactory nodules in Korea, an iodine-sufficient area.
Highlights
For individuals with thyroid nodules, ultrasound (US) is a primary diagnostic modality to evaluate the risk of malignancy (ROM) and to inform decisions regarding the application of fine-needle aspiration (FNA) [1]
The Institutional Review Board (IRB) waived the requirement for informed consent because all data were deidentified
The possibility of ROM overestimation due to selection bias should be considered since nodules without histopathological or cytological follow-up, those without even radiological follow-up, are more likely to be cases with low clinical suspicion
Summary
For individuals with thyroid nodules, ultrasound (US) is a primary diagnostic modality to evaluate the risk of malignancy (ROM) and to inform decisions regarding the application of fine-needle aspiration (FNA) [1]. For some of these USbased risk stratification systems (RSSs), the terminology of the Thyroid Imaging, Reporting and Data System (TIRADS) has been used [3] These US-based RSSs include the nodule sonographic pattern system proposed by the 2015 revised American Thyroid Association (ATA) guidelines [4], the Korean TIRADS (K-TIRADS) by the Korean Thyroid Association (KTA)/Korean Society of Thyroid Radiology (KSThR) in 2016 [1,2], the European (EU)TIRADS by the European Thyroid Association (ETA) in 2017 [5], and the American College of Radiology (ACR) TIRADS in 2017 [3]. A meta-analysis reported better performance for the ACR TIRADS than the ATA nodule sonographic pattern system or K-TIRADS in selecting nodules for FNA, comparisons across the commonly used systems were limited by the limited data availability [8]
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