A Comparison of Two Widely Used Risk Stratification Systems for Thyroid Nodule Sonographic Evaluation.

BACKGROUND The 2015 American Thyroid Association (ATA2015) and the American College of Radiology Thyroid Imaging and Reporting Data System (ACR TI-RADS) are two widely used thyroid sonographic systems. OBJECTIVES To compare the two systems for accuracy of cancer risk prediction. METHODS Preoperative ultrasound images from 265 patients who underwent thyroidectomy at our hospital from January 2012 to March 2019 were retrospectively categorized by the ACR TI-RADS and ATA2015 systems. Diagnostic performances were compared. RESULTS Of 238 nodules assessed, 115 were malignant. Malignancy risks for the five ACR TI-RADS categories were 0%, 7.5%, 11.4%, 59.6%, and 90.0%. Malignancy risks for the five ATA2015 categories were 0%, 6.8%, 17.0%, 55.5%, and 92.1%. The proportion of total nodules biopsied was higher with the ATA2015 system than the ACR TI-RADS system: 88.7% vs. 66.3%. Proportions of malignant nodules and benign nodules biopsied were higher with ATA2015 than with ACR TI-RADS: 93.3% vs. 87.8% and 84.4% vs. 46.3%, respectively. Specificity and sensitivity rates were 53.6% and 84.3%, respectively, for ACR TI-RADS, and 15.5% and 93.3%, respectively, for ATA2015. The two systems showed similarly accurate diagnostic performance (AUC > 0.88). False negative rates for ACR TI-RADS and ATA2015 were 15.6% and 6.6%, respectively. Rates of missed aggressive cancer were similar for the two systems: 3.4% and 3.7%, respectively. CONCLUSIONS ACR TI-RADS was superior to ATA2015 in specificity and avoiding unnecessary biopsies. ATA2015 yielded better sensitivity and a lower false negative rate. Identification of aggressive cancers was identical in the two systems.