Nodules with nonspecific ultrasound pattern according to the 2015 American Thyroid Association malignancy risk stratification system A comparison to the Thyroid Imaging Reporting and Data System (TIRADS-Na)

New sonographic patterns have been recommended by the 2015 American Thyroid Association (ATA) to stratify nodules in terms of malignancy risk and help guide biopsy decision. This study aimed to compare the ultrasound part of the ATA guidelines and the Thyroid Imaging Reporting and Data System (TIRADS-Na). In 2013 to 2016, 708 thyroid nodules in 505 patients were confirmed by postoperative histopathology. Hypoechogenicity, solidity, microcalcification, irregular margin, and a taller-than-wide shape were considered features suggesting malignancy. Sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) were obtained for the TIRADS and ATA guidelines. Of the 708 nodules, 341(48.2%) and 367(51.8%) were benign and malignant, respectively. Based on the ultrasound 2015 ATA guidelines, 62 nodules had nonspecific pattern (both malignant and benign features); malignancy rates of nodules with very low, low, intermediate, and high suspicion, and nonspecific pattern were 0, 17.7%, 57.9%, 90.0%, and 69.4%, respectively (P<.001). Malignancy rates of categories 2/3/4/5 nodules by TIRADS were 0, 8.1%, 67.0%, and 90.1%, respectively (P<.001). Based on pathological results, the AUC, sensitivity, specificity, NPV, and PPV were 0.926, 96.7%, 81.5%, 84.9%, and 95.9% for TIRADS, and 0.920, 93.5%, 82.4%, 85.1%, and 92.1% for ATA patterns, respectively. The TIRADS was generally more efficient than the 2015 ATA guidelines, especially for nodules >2cm in diameter or those with nonspecific pattern. The TIRADS show a relative superiority over the ultrasound 2015 ATA guidelines, especially for nodules with >2cm diameter or nonspecific pattern.