A DIRECT COMPARISON OF THE ATA AND TI-RADS ULTRASOUND SCORING SYSTEMS.

Objective: This study compares the American Thyroid Association (ATA) classification system with the 2017 American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TI-RADS) for predicting cancer risk in thyroid nodules. Methods: This is a retrospective review of ultrasound imaging of all adult patients with thyroid nodules >5 mm who underwent thyroidectomy at a tertiary care hospital in 2016. We assessed the ability of either system to predict malignancy based on surgical histopathology. Sensitivity, specificity, negative predictive values (NPV) and positive predictive values (PPV), and area-under-the-curve (AUC) were calculated and compared using McNemar's, Fisher exact, or DeLong's tests. Results: Three hundred and twenty-three nodules from 213 adults were included. Median patient age was 55 years; 75.6% were female. 27.2% nodules were malignant. Both ATA and ACR TI-RADS provide effective diagnostic performance, a sensitivity of 77.3% versus 78.4%, respectively, a specificity of 76.6% versus 73.2%, respectively, a PPV of 55.3% versus 52.3%, respectively, and a NPV of 90% for both. The level of agreement between the two classification systems was almost perfect (weighted Kappa statistic = 0.93, AUC 0.77 ATA versus 0.76 TI-RADS [ P = .18]). However, of the 40 (TI-RADS level 3) TR3 nodules (<2.5 cm), 10% were malignant, and of the 31 (TI-RADS level 4) TR4 nodules (<1.5 cm), 38% were malignant. Conclusion: The ATA and TI-RADS classification systems appear to have similar diagnostic value for predicting thyroid cancer. However, subanalysis of TR3 and TR4 nodules with consideration of size criteria showed that there is a higher risk of missing a malignancy if the ACR TI-RADS recommendation is followed. These results should be validated in a different patient cohort with a lower incidence of cancer. Abbreviations: ACR = American College of Radiology; ATA = American Thyroid Association; FNA = Fine Needle Aspiration; κ = weighted Kappa statistic; NPV = negative predictive values; PPV = positive predictive values; TI-RADS = Thyroid Imaging Reporting and Data System; TR1 = TI-RADS level 1; TR2 = TI-RADS level 2; TR3 = TI-RADS level 3; TR4 = TI-RADS level 4; TR5 = TI-RADS level 5.