Abstract
BACKGROUND: Detection of synovitis is essential for assessing rheumatoid arthritis (RA) activity and predicting prognosis. This study aimed to compare the diagnostic performance of superb microvascular imaging (SMI) with that of contrast-enhanced ultrasound (CEUS) in patients with RA in clinical remission. METHODS: SMI and CEUS were applied to 63 patients with active RA and 48 patients with RA in clinical remission. Differences in positive synovial vascularity (SV) and its semi-quantitative scale were observed, and the correlations of SMI and CEUS results with C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and rheumatoid factor (RF) were analyzed. RESULTS: For the 63 joints with active RA, the detection rates of SV as determined by SMI and CEUS were 90.5% (95% CI: 83.0-97.9%) and 93.7% (95% CI: 87.5-99.8%), respectively, with no significant difference observed between the two modalities (t=-1.137; P=0.260). There was good agreement between the two modalities in detecting positive blood flow (Kappa =0.784) and blood flow signal score (Kappa =0.792). For the 48 joints with clinical remission, the detection rates of SV determined by SMI and CEUS were 79.2% (95% CI: 67.2-91.1%) and 83.3% (95% CI: 72.4-94.3%), respectively, with no significant difference found between the two modalities (t=1.000; P=0.322). There was high consistency between the two modalities in detecting positive blood flow (Kappa =0.727) and blood flow signal score (Kappa =0.661). The vascularity scores of SMI and CEUS were positively correlated with CRP, ESR, and RF in the joints with active RA, but not in those with clinical remission. CONCLUSIONS: SMI is as sensitive as CEUS for detecting vessels in the synovium and displaying local SV in patients with RA who achieve clinical remission.