• Suh Young Kim, Dong Gyu Na, and Wooyul Paik.
• Department of Radiology, Gangneung Asan Hospital, University of Ulsan College of Medicine, 38 Bangdong-gil, Sacheon-myeon, Gangneung-si, Gangwon-do, 25440, Republic of Korea.
• Eur Radiol. 2021 Oct 1; 31 (10): 7605-7613.

ObjectivesThis study aimed to determine the ultrasound (US) image plane appropriate for evaluating the taller-than-wide (TTW) sign in the risk stratification of thyroid nodules using the five widely used risk stratification systems (RSSs).MethodsA total of 1905 consecutive thyroid nodules with final diagnoses were included. The TTW sign was prospectively assessed in the transverse and longitudinal US image planes. The diagnostic performances of the TTW sign and biopsy criteria by the RSSs for malignancy were compared by sensitivity, specificity, and receiver operating characteristic curve analysis between the two criteria of TTW signs according to image planes (criterion 1, transverse plane; criterion 2, either transverse or longitudinal plane).ResultsOf all 1905 nodules, 1481 (77.7%) were benign and 424 (22.3%) were malignant. The criteria 1 and 2 of TTW signs had similar sensitivities (37.5% and 38.7%) and specificities (94.8% and 94.4%) with minimal differences, and the area under the curve (AUC) of TTW signs for malignancy was not significantly different between criteria 1 and 2 (0.662 and 0.665, p = 0.158, respectively). The sensitivity, specificity, and AUC of biopsy criteria by the five RSSs were not significantly different between criteria 1 and 2 in nodules ≥ 1 cm (p ≥ 0.157, p ≥ 0.317, and p ≥ 0.198, respectively).ConclusionsThe diagnostic performances of the TTW sign and biopsy criteria of the five RSSs were similar between criteria 1 and 2. TTW signs by criterion 1 (transverse plane) may be appropriate in the risk stratification of thyroid nodules.Key Points• The diagnostic performance of the taller-than-wide sign by ROC analysis was not significantly different between US image plane criteria (transverse plane vs. either transverse or longitudinal plane). • The diagnostic performances of biopsy criteria for malignancy by the five risk stratification systems were similar between the two taller-than-wide sign criteria. • The taller-than-wide sign using the transverse plane may be appropriate in the risk stratification of thyroid nodules.© 2021. European Society of Radiology.

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