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.