A Single-Center Retrospective Validation Study of the American College of Radiology Thyroid Imaging Reporting and Data System

Objective This study aimed to evaluate a new risk stratification system, the American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TI-RADS), published in 2017. Materials and Methods From January 2015 to December 2016, 1033 thyroid nodules in 1013 patients who had undergone sonography and thyroid surgery or fine-needle aspiration (FNA) in our hospital were included. The sonographic features were described in a standard manner and analyzed according to the white paper of the ACR TI-RADS Committee. Nodules were assigned points for each feature, and the points were totaled to determine the final TI-RADS levels. Results Of the 1033 nodules, 725 were benign and 308 were malignant proven by operation or FNA. The malignant risk was associated with the composition, echogenicity, shape, margins, and echogenic foci of the nodules (P < 0.001). The calculated risk of malignancy was higher in nodules with macrocalcifications than those with peripheral calcifications, which is different from the ACR TI-RADS. The calculated malignancy rates of nodules with TR5, TR4, TR3, and TR2 were 67.1%, 13.0%, 1.1%, and 0%, respectively, which showed a higher malignant risk than the suggested threshold of TR5 in the ACR TI-RADS. Six nodules with TR4 recommended for no follow-up and 55 nodules with TR5 recommended for follow-up were malignant with cervical lymph node metastasis. Conclusions The ACR TI-RADS provides effective malignancy risk stratification for thyroid nodules and was useful for the decision for FNA. However, the points assigned for echogenic foci, the set of the TI-RADS risk thresholds, and FNA thresholds may need more consideration and prospective validation.