Abstract
Ultrasonographic (US) assessment methods may affect the estimated malignancy risk of thyroid nodules. This study aimed to investigate the impact of retrospective and prospective US assessments on the estimated malignancy risk of US features, classified categories, and diagnostic performance of five risk stratification systems (RSSs) in thyroid nodules. A total of 3685 consecutive thyroid nodules (≥1 cm) with final diagnoses (retrospective dataset, n = 2180; prospective dataset, n = 1505) were included in this study. We compared the estimated malignancy risk of US features, classified categories, and diagnostic performances of the five common RSSs between retrospective (static US images without cine clips) and prospective datasets of real-time US assessment. There was no significant difference in the prevalence and histological type of malignant tumours between the two datasets (p ≥ 0.216). The malignancy risk of solid composition and nonparallel orientation was higher and that of microcalcification was lower in the prospective dataset than in the retrospective dataset (p < 0.001, p = 0.018, p = 0.007, respectively). The retrospective US assessment showed slightly higher malignancy risk of intermediate- or high-risk nodules according to the RSSs. Prospective US assessment showed lower specificities and higher unnecessary biopsy rates by all RSSs compared to the retrospective US assessment (p ≤ 0.006, p ≤ 0.045, respectively). The retrospective US assessment showed higher malignancy risk of microcalcification and some classified categories by RSSs, and overestimated the specificities and underestimated the unnecessary biopsy rates by all RSSs compared to prospective US assessment.
Highlights
Ultrasonography (US) is an established primary diagnostic tool that has been widely used to predict malignancy risk of thyroid nodules [1]
The malignancy risk of solid composition and nonparallel orientation was higher and that of microcalcification was lower in the prospective dataset than in the retrospective dataset (p < 0.001, p = 0.018, p = 0.007, respectively)
We aimed to evaluate the impact of assessment method on classified categories of nodules by the risk stratification systems (RSSs) and diagnostic performance of biopsy criteria for malignancy by the widely used five US RSSs, including the American Thyroid Association (ATA) system, American Association of Clinical Endocrinologists/American College of Endocrinology/Associazione Medici Endocrinologi (AACE/ACE/AME) system, Korean Thyroid Imaging Reporting and Data System (K-TIRADS), American College of Radiology (ACR) TI-RADS, European (EU)TIRADS [3,4,5,6,7]
Summary
Ultrasonography (US) is an established primary diagnostic tool that has been widely used to predict malignancy risk of thyroid nodules [1]. Many international societies have proposed US risk stratification systems (RSSs) for thyroid nodules [2,3,4,5,6,7], which have been validated by multiple studies based on either retrospective assessment with or without cine clips [8,9,10,11,12] or prospective US assessment of nodules [13,14,15]. Careful US assessment will enable accurate prediction of malignancy risk of nodules and provide a reliable basis for the development of US RSS for thyroid nodules. To the best of our knowledge, few studies have investigated the impact of retrospective and prospective US assessments on the estimated malignancy risk of US features and diagnostic performance of RSSs in thyroid nodules. A comparison of results between studies according to the method of US assessment (retrospective or prospective) for thyroid nodules may not provide accurate information on the differences resulting from the US assessment method because of uncontrolled confounding factors such as differences in study populations, interpreters, and applied definitions of US lexicons
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