Differences between ATA, AACE/ACE/AME and ACR TI-RADS ultrasound classifications performance in identifying...

Thyroid ultrasound is crucial for clinical decision in the management of thyroid nodules. In this study, we aimed to estimate and compare the performance of ATA, AACE/ACE/AME and ACR TI-RADS ultrasound classifications in discriminating nodules with high-risk cytology.

Cross-sectional study.

1077 thyroid nodules undergoing fine-needle aspiration were classified according to ATA, AACE/ACE/AME and ACR TI-RADS ultrasound classifications by an automated algorithm. Odds ratios (ORs) and receiver operating characteristic (ROC) curves for high-risk cytology categories (TIR3b, TIR4 and TIR5) were calculated for the different US categories and compared.

Cytological categories of risk increased together with all US classifications' sonographic patterns (P < 0.001). The diagnostic performance (C-index) of ACR TI-RADS and AACE/ACE/AME significantly improved when adding clinical data as gender and age in the regression model (P < 0.001). A significant difference in the final model C-index between the three US classification systems was found (P < 0.029), with the ACR TI-RADS showing the highest nominal C-index value, significantly superior to ATA (P = 0.008), but similar to AACE/ACE/AME (P = 0.287). ATA classification was not able to classify 54 nodules, which showed a significant 7 times higher risk of high-risk cytology than the 'very low suspicion' nodules (OR: 7.20 (95% confidence interval: 2.44-21.24), P < 0.001).

The ACR TI-RADS classification system has the highest area under the ROC curve for the identification of cytological high-risk nodules. ATA classification leaves 'unclassified' nodules at relatively high risk of malignancy.