This study evaluated Superb Microvascular Imaging (SMI) technology for detection of active synovitis in patients with rheumatoid arthritis (RA).
Between June 2015 and October 2016, 56 patients with RA (42 females; mean age, 53.2 years) underwent gray-scale ultrasound (US) imaging, power Doppler imaging (PDI), and SMI for synovitis of both wrists and hands (total 22 joints), scored for each joint from grades 0 to 3. The sum of grades for 22 joints was determined for gray-scale (SYN-sum), PDI (PDI-sum), and SMI (SMI-sum) according to clinical parameters. Follow-up US was performed in 17 patients (mean interval, 251.6 days).
The SMI-sum (7.27 ± 4.56) was significantly higher than the PDI-sum (4.38 ± 3.09, p < 0.001) and the SYN-sum (4.55 ± 3.72, p < 0.001), and was significantly correlated with the erythrocyte sedimentation rate, C-reactive protein (CRP), and Disease Activity Score-28 (DAS28)-CRP (γ = 0.409, p = 0.002; γ = 0.695, p < 0.001; γ = 0.726, p < 0.001, respectively). Moreover, in 28 patients with clinical remission, the SMI-sum (4.32 ± 2.01) was greater than the PDI-sum (2.61 ± 1.60, p < 0.001). In 17 patients with follow-up US, the SMI-sum (2.35 ± 1.73) was significantly greater than the PDI-sum (1.24 ± 1.20; p < 0.001) and was also significantly correlated with DAS28 (γ = 0.880).
• SMI correlated well with PDI and was more sensitive for detection of active synovitis in RA. • The SMI-sum was not only of greater value but also more strongly correlated than the PDI-sum with clinical inflammatory indicators including ESR, CRP, and DAS28 on initial and follow-up US examinations. • The SMI-sum was even significantly increased in patients with clinical remission.
SMI may detect active synovitis with greater sensitivity than PDI in RA patients, even with clinical remission, and is well-correlated with inflammatory parameters during follow-up.