Performance of EU-TIRADS in malignancy risk stratification of thyroid nodules. A meta-analysis

Objective: Several thyroid imaging reporting and data systems (TIRADS) have been proposed to stratify the malignancy risk of thyroid nodule by ultrasound. The TIRADS by the European Thyroid Association, namely EU-TIRADS, was the last one to be published. Design: We conducted a meta-analysis to assess the prevalence of malignancy in each EU-TIRADS class and the performance of EU-TIRADS class 5 versus 2, 3 and 4 in detecting malignant lesions. Methods: Four databases were searched until December 2019. Original articles reporting the performance of EU-TIRADS and adopting histology as reference standard were included. The number of malignant nodules in each class and the number of nodules classified as true/false positive/negative were extracted. A random-effects model was used for pooling data. Results: Seven studies were included, evaluating 5,672 thyroid nodules. The prevalence of malignancy in each EU-TIRADS class was 0.5% (95%CI 0.0-1.3), 5.9% (95%CI 2.6-9.2), 21.4% (95%CI 11.1-31.7), and 76.1% (95%CI 63.7-88.5). Sensitivity, specificity, PPV, NPV, LR+, LR- and DOR of EU-TIRADS class 5 were 83.5% (95%CI 74.5-89.8), 84.3% (95%CI 66.2-93.7), 76.1% (95%CI 63.7-88.5), 85.4% (95%CI 79.1-91.8), 4.9 (95%CI 2.9-8.2), 0.2 (95%CI 0.1-0.3), and 24.5 (95%CI 11.7-51.0), respectively. A further improved performance was found after excluding two studies because of limited sample size and low prevalence of malignancy in class 5. Conclusions: A limited number of studies generally conducted using a retrospective design was found. Acknowledging this limitation, the performance of EU-TIRADS in stratifying the risk of thyroid nodules was high. Also, EU-TIRADS class 5 showed moderate evidence of detecting malignant lesions.