To compare the diagnostic value of the American College of Radiology thyroid imaging reporting and data system (ACR TI-RADS) and Chinese thyroid imaging reporting and data system (C-TIRADS) in thyroid micronodules.

A total of 1213 patients with 1599 thyroid micronodules confirmed by surgical pathology were enrolled. According to the ACR TI-RADS and C-TIRADS, thyroid micronodules were evaluated and scored. Using surgical pathology as the golden standard, a ROC curve was constructed to determine the optimal cut-off value. Nodules with scores above the cutoff were classified as malignant, while those below as benign. The diagnostic efficacy of ACR TI-RADS and C-TIRADS systems for thyroid microcarcinomas was then analyzed and compared by DeLong test.

Both ACR TI-RADS and C-TIRADS scores and classifications of malignant nodules were higher than those of benign nodules (P＜0.05), with AUC values being 0.702, 0.658, 0.710, and 0.686, respectively. The DeLong test shows the AUC values of the scoring systems were greater than those of the classification systems (Z=3.768 and 2.370, respectively, P=0.0002 and 0.0178, respectively). When the Youden index was the largest, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the ACR TI-RADS system were 89.66%, 41.70%, 89.93%, and 59.00%, respectively; and the corresponding values of the C-TIRADS system were 88.71%, 44.26%, 90.23%, and 59.69%, with no statistically significant differences between the two systems (χ²=0.642, 0.313, 0.070, and 0.025, respectively, P=0.423, 0.576, 0.791, and 0.875, respectively).

Although the ACR TI-RADS and C-TIRADS scoring systems demonstrate superior diagnostic efficacy compared to their classification counterparts, their overall performance remains suboptimal, which may compromise the diagnostic accuracy for thyroid nodules to some extent.