The Impact of Echogenicity Grading on the Diagnostic Performance of C-TIRADS.

Purpose: To investigate whether echogenicity grading can improve the diagnostic performance of the Chinese Thyroid Imaging Reporting and Data System (C-TIRADS).

Patients and methods: Ultrasonic (US) images of 646 thyroid nodules (TNs) were retrospectively reviewed. The sonographic features of each nodule were analyzed and noted, including the orientation, margin, composition, echogenicity, echogenic foci, and extrathyroidal extension. Hypoechoic was further graded as mildly, moderately and markedly hypoechoic, and the malignancy risk at different echogenicity levels was compared. Each nodule was categorized according to C-TIRADS using markedly hypoechoic, modified markedly hypoechoic, and hypoechoic as malignant indicators, and the classification results were recorded as TI-RADS 1, 2, and 3, respectively. The diagnostic sensitivity, specificity, and area under the curve (AUC) of the different echogenicity and TIRADS were compared using chi-square analysis and Receiver Operating Characteristic curves (ROC). Binary logistic regression analysis was used to calculate cancer risk for different echogenicity. The interobserver agreement in the grading of echogenic of the nodules was also assessed.

Results: Most malignant nodules were hypoechoic (85.2%), and the malignancy risk of hypoechoic nodules was significantly higher than that of iso-hyperechoic nodules (34.4% vs 9.8%). The malignancy risk gradually increased as nodule echogenicity decreased (odd ratios (ORs) of 2.132, 10.009, and 15.006, respectively). There was no significant difference in the malignancy risk between moderately and markedly hypoechoic nodules (P=0.203). The modified markedly hypoechoic region showed the highest AUC and the most balanced sensitivity and specificity for the diagnosis of thyroid cancer. The diagnostic performance of TI-RADS 2 was significantly higher than that of TI-RADS 1 and 3 (AUC of 0.715, 0.608, and 0.656, respectively). Substantial agreement was obtained between the two observers in grading markedly hypoechoic and modified markedly hypoechoic (κ = 0.79 and 0.75; 95% CI: 0.75,0.83 and 0.64,0.86).

Conclusion: Stratifying hypoechogenic to three degrees enhances confidence in evaluating malignancy risk. Compared to markedly hypoechoic, the modified markedly hypoechoic significantly boosted the ability of C-TIRADS to differentiate benign TNs from malignant ones.