Diagnostic value of greyscale ultrasound combined with superb microvascular imaging in thyroid nodules: a systematic review and meta-analysis.

Background: Superb microvascular imaging (SMI) is an advanced form of Doppler flow imaging which has advantages in tiny vessels and low-speed flow. This study aimed to evaluate the diagnostic performance of combining greyscale ultrasound (US) with SMI in differentiating between benign and malignant thyroid nodules.

Methods: A search was conducted in PubMed, Embase, Cochrane Library, Scopus, and Web of Science for relevant studies published till 25 October 2023 that investigated the combined use of greyscale US and SMI to differentiate between benign and malignant thyroid nodules. A subgroup analysis was performed on the basis of different SMI diagnostic criteria for malignant thyroid nodules. The Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) was used for quality assessment. The summary sensitivity, specificity, positive likelihood ratio (LR), negative likelihood ratio (LR), diagnostic odds ratio (DOR), and summary receiver operating characteristic (SROC) curve were used for evaluation of diagnostic performance.

Results: A total of 10 original studies, encompassing 1,160 thyroid nodules, 556 of which were malignant, were included in the analysis. The area under the curve (AUC) of greyscale US combined with SMI in diagnosing malignant thyroid nodules was 0.92 [95% confidence interval (CI): 0.89-0.94]. The summary sensitivity and specificity were 0.90 (95% CI: 0.77-0.96) and 0.74 (95% CI: 0.54-0.88) for greyscale US combined with rich vascularity on SMI, 0.86 (95% CI: 0.76-0.92) and 0.83 (95% CI: 0.71-0.91) for greyscale US combined with vascular distribution on SMI, 0.87 (95% CI: 0.80-0.92) and 0.88 (95% CI: 0.81-0.93) for greyscale US combined with the penetrating vessel on SMI, respectively. Meta-regression analysis revealed that variations in sample size could be a source of heterogeneity.

Conclusions: Although the SMI diagnostic criteria for malignant nodules varied among the studies, the combination of greyscale US with SMI demonstrates great diagnostic performance for the differentiation of benign and malignant thyroid nodules. However, more studies are still needed on the standardized SMI diagnostic criteria for thyroid nodules.