Interrater Reliability of Various Thyroid Imaging Reporting and Data System (TIRADS) Classifications for Differentiating Benign from Malignant Thyroid Nodules

Abstract

Background: Thyroid ultrasound(US) is used as the first diagnostic tool to assess the management of disease but<br />is operator dependent. There have been few reports evaluating interrater variability in US assessment. Therefore, we<br />evaluated interrater reliability in US assessment of thyroid nodules and estimated its diagnostic accuracy for various<br />TIRADS systems. Methods: This retrospective study included 24 malignant nodules and 84 benign nodules from<br />January 2015 to October 2017. Two blinded observers independently reviewed stored US images by using TIRADS. All<br />analyses followed guidelines proposed by ACR-TR, Siriraj-TR and EU-TR systems. Interrater reliability was calculated<br />using Cohen's Kappa statistics. Diagnostic accuracy were also calculated. Results: Interobserver agreement showed<br />substantial agreement for composition (K=0.616); echogenicity and echogenic foci showed fair agreement (K=0.327<br />and 0.288, respectively); margin showed slight agreement (K=0.143). Interrater reliability for the final assessment;<br />moderate agreement for ACR-TIRADS system (K=0.500); fair agreement for EU-TIRADS system (K=0.209) and<br />slight agreement (K=0.114) for Siriraj-TIRADS system. The diagnostic performance from the two observers; ACRTIRADS<br />system; sensitivities were 75% and 79.2%, specificities were 58.3% and 56%, positive predictive value (PPV)<br />were 34% and 33.9% and negative predictive value (NPV) were 89.1% and 90.4%. For the Siriraj-TIRADS system,<br />sensitivities were 41.7% and 25%, specificities were 84.5% and 89.3%, positive predictive value (PPV) were 43.5%<br />and 40% and negative predictive value (NPV) were 83.5% and 80.6%. For the EU-TIRADS system, sensitivities were<br />45.8% and 66.7%, specificities were 79.8% and 72.6%, positive predictive value (PPV) were 39.3% and 41% and<br />negative predictive value (NPV) were 83.8% and 88.4%. Conclusion: The ACR-TIRADS had highest interobserver<br />agreement, a trend to have highest sensitivity and negative predictive value for diagnosis of malignant thyroid nodules.<br />Siriraj-TIRADS had higher specificity and accuracy, but