Retrospective Cohort Study of 1947 Thyroid Nodules: A Comparison of the 2017 American College of Radiology TI-RADS and the 2015 American Thyroid Association Classifications.

Abstract

<b>OBJECTIVE.</b> The objective of our study was to compare diagnostic accuracy and reliability of the 2017 American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TI-RADS) and 2015 American Thyroid Association (ATA) classifications for thyroid nodules. <b>MATERIALS AND METHODS.</b> This study was a retrospective cohort study of 1947 consecutive thyroid nodules sampled with fine-needle aspiration (FNA) from 2007 to 2016. Reviewers assigned TI-RADS scores to all nodules while blinded to clinical outcome and histologic diagnosis and compared TI-RADS scores with nodule-specific ATA scores from the same cohort. Five blinded radiologists independently assigned TI-RADS scores to a subset of 151 nodules (interrater agreement). The primary outcome was a comparison of the diagnostic accuracy of the TI-RADS and ATA classifications using ROC curve analysis. The reference standard was cytopathologic diagnosis according to the Bethesda system. Interrater agreement was determined using intraclass correlation (ICC) and kappa statistics. <b>RESULTS.</b> Of 1947 sampled thyroid nodules, 31.8% (<i>n</i> = 620) met TI-RADS criteria for FNA, 28.0% (<i>n</i> = 545) met TI-RADS criteria for follow-up, and 40.2% (<i>n</i> = 782) met TIRADS criteria to be ignored. Applying the 2015 ATA criteria resulted in recommendations of immediate FNA procedures for more nodules than applying the 2017 TI-RADS (ATA vs TIRADS: 62.3% [1213/1947] vs 31.8% [620/1947], <i>p</i> < 0.0001). Diagnostic accuracies (AUCs: TI-RADS score, 0.684 [95% CI, 0.644-0.724]; ATA, 0.686 [95% CI, 0.646-0.725]) and false-negative rates (TI-RADS, 2.2% [43/1947]; ATA, 2.4% [47/1947]) for the two classifications were similar (<i>p</i> = 0.75). Overall interrater agreement was fair for both (ICCs: TI-RADS, 0.437 [95% CI, 0.357-0.520]; ATA classification, 0.460 [95% CI, 0.391-0.533]). <b>CONCLUSION.</b> The 2017 ACR TI-RADS and 2015 ATA classifications have similar diagnostic accuracies and interrater agreement, but TI-RADS results in fewer nodules being recommended for immediate FNAs and more nodules being recommended for imaging surveillance.