Impact of thyroid nodule sizes on the diagnostic performance of Korean thyroid imaging reporting and data system and contrast-enhanced ultrasound

OBJECTIVE: This study aimed to evaluate the impact of thyroid nodule sizes on the diagnostic performance of Korean thyroid imaging reporting and data system (TIRADS) and contrast-enhanced ultrasound (CEUS). METHODS: In total, 308 consecutive patients with 382 thyroid nodules underwent US-guided FNA or surgery were included in this retrospective study. The nodule size was classified into 3 categories: <= 10 mm (group A), 10-20 mm (group B), and >= 20 mm (group C). We compared the risk of malignancy in each subgroup, categorized according to the TIRADS and CEUS patterns. RESULTS: In group A, the differences in diagnostic value between TIRADS and CEUS were significant (AUC: 0.804 vs 0.733, P = 0.028, sensitivity: 81.8% vs 72.7%, P = 0.013, specificity: 88.9% vs 79.4%, P = 0.011). In group B, the AUC (0.897), sensitivity (88.1%) and specificity (91.9%) of CEUS were highest. In group C, the specificity of CEUS was significantly higher compared with TIRADS classification (90.8% vs 82.9%, P = 0.023), while the sensitivity and AUC showed no significant difference between the two models (84.2% vs 81.5%, P> 0.406, 0.848 vs 0.820, P= 0.545). CONCLUSIONS: Nodule size influences the diagnostic accuracy of the two methods. TIRADS have best value in nodules <= 10 mm, while CEUS perform best for differentiating lesions >10 mm, especially in lesions >= 20 mm.