Head-to-head comparison of American, European, and Asian TIRADSs in Thyroid Nodule Assessment: Systematic Review and Meta-Analysis

Context Ultrasound-based risk stratification systems (TIRADSs) of thyroid nodules (TNs) have been implemented in clinical practice worldwide, based on their high performance. However, it remains unexplored whether different TIRADSs perform uniformly across a range of TNs in routine practice. This issue is highly relevant today, given the ongoing international effort to establish a unified TIRADS (i.e. I-TIRADS), supported by the leading societies specializing in TNs. The study aim was to conduct a direct comparison among ACR-, EU-, and K-TIRADS in the distribution of TNs: 1) across the TIRADS categories, and 2) based on their estimated cancer risk. Methods A search was conducted on Pubmed and Embase until June 2023. Original studies that sequentially assessed TNs using TIRADSs, regardless of FNAC indication, were selected. General study characteristics and data of distribution of TNs across TIRADSs were extracted. Results Seven studies, reporting a total of 41,332 TNs, were included in the analysis. The prevalence of ACR-TIRADS 1-2 was significantly higher than that of EU-TIRADS 2 and K-TIRADS 2, with no significant difference observed among intermediate- and high-risk categories of TIRADSs. According to malignancy risk estimation, K-TIRADS often classified TNs as having more severe risk, ACR-TIRADS as moderate risk, while EU-TIRADS classified TNs as lower risk. Conclusions ACR-, EU-, and K-TIRADS assess TNs similarly across their categories, with slight differences in low-risk classifications. Despite this, focusing on cancer risk estimation, the three TIRADSs assess TNs differently. These figures should be considered as prerequisite for developing the I-TIRADS.