PURPOSE: To investigate the concordance of ultrasonography (US) classified nodules and the impact of biopsy size thresholds on diagnostic performance for thyroid malignancy among three international guidelines of Korean Thyroid Association/ Korean Society of Thyroid Radiology (KTA/KSThR), American Thyroid Association (ATA), and American College of Radiology (ACR).
MATERIALS AND METHODS: A total of 2,586 thyroid nodules (≥ 1 cm) were retrospectively collected from two multicenter study datasets. Thyroid nodules were classified according to US categories of nodules for malignancy risk by the three guidelines. Concordance rate of classified nodules among three different guidelines was calculated. Diagnostic performance of biopsy size criteria was evaluated by using the simulated four different biopsy size criteria.
RESULT: Concordance rate of high or intermediate suspicion nodules was high (84.1-100%), however, low or mildly suspicious nodules showed a relatively low concordance rate (63.8-83.8%) among the three guidelines. The differences of sensitivity, specificity, and accuracy among the guidelines were 0.7 - 19.8%, 0 - 40.9%, and 0.1 - 30.5% with original biopsy criteria, which decreased to 0 - 5.9%, 0 - 10.9%, and 0.1 - 8.2% with simulated similar biopsy size criteria, respectively. The difference of unnecessary biopsy rate with original biopsy criteria (0-33.8 %) decreased with simulated biopsy size criteria (0-8.7%).
CONCLUSION: Concordance rate of high or intermediate suspicion nodules is high among the three guidelines. The difference in the diagnostic performance of the guidelines is mainly influenced by the different size thresholds for biopsy and partly by the different US categorization system of thyroid nodules.