Introduction: Shear-wave elastographic ultrasound (SW-EUS) assesses the stiffness of human tissues. It is used in liver, thyroid and breast imaging but has not been studied in synovium. Soft tissues have a slower shear-wave velocity (SWV) than stiff tissues. We hypothesised that rheumatoid arthritis (RA) patients would have softer synovium than controls and this could be quantified with a slower SWV. We also assessed whether SWV varied with disease activity. Methods: Nine patients with RA were consecutively recruited and matched with five controls. Participants underwent clinical assessment, blood sampling, grey scale ultrasound (GSUS), power Doppler ultrasound and SW-EUS of MCP joints 2-5 on the dominant hand. Results: Average age was 60. Mean RA disease activity (DAS28-ESR) was moderate at 3.65. Patients with RA had lower maximum synovial SWV than controls (6.38 m/s vs. 6.99 m/s P = 0.042). Negative Pearson's correlation coefficients (PCC) were observed between maximum SWV and disease activity markers including GSUS graded synovial thickness (PCC = À0.57, P = 0.03) and ESR (PCC = À0.46, P = 0.095). Intra-and interobserver reliability was good with intraclass correlation coefficients (ICC) of 0.66 and 0.58, respectively, for quantitative maximum SWV and ICC > 0.80 for colour scale rated SWV. Conclusion: This is the first pilot study of SW-EUS in synovium. Maximum synovial SWV was significantly lower in RA than controls. There was a negative correlation between maximum SWV and GSUS synovial thickening. Further study is warranted to confirm the role of SW-EUS in diagnosing and assessing disease activity in RA.

BackgroundShear wave elastographic ultrasound (SW-EUS) assesses the stiffness of human tissues. It is used in liver, thyroid and breast imaging but has never before been studied in synovium. Soft tissues have a slower shear wave velocity (SWV) than stiff tissues. We hypothesised that rheumatoid arthritis (RA) patients would have softer synovium and thus slower SWV than controls.ObjectivesThe aim of the project was to establish a reproducible scoring system for synovial SW-EUS and use it to compare RA patients with controls. We also set out to assess if SWV varied with disease activity.MethodsA cross sectional study was conducted including nine RA patients and five age and sex matched controls. RA patients were recruited consecutively from a single rheumatology practice. Participants underwent a questionnaire, clinical examination, blood sampling, grey scale ultrasound (GSUS), power doppler ultrasound and SW-EUS ultrasound examination of MCP joints 2 - 5 on the dominant hand. Ultrasound was performed and scored by two blinded musculoskeletal trained sonographers.ResultsThe average age of participants was 60. The mean RA disease activity score (DAS28-ESR) was in the low to moderate range of 3.65 (range 2.4–7.4). Patients with RA had significantly lower maximum SWV than controls (6.38 m/s vs 6.99 m/s p=0.042). Negative Pearson's correlation coefficients (PCC) were observed between maximum SWV and a range of disease activity markers including GSUS graded synovial thickness (PCC = -0.57, p=0.03) and ESR (PCC = -0.46, p=0.095). SW-EUS had good intra- and inter-observer reliability with intraclass correlation coefficients of 0.66 and 0.58 for maximum SWV and >0.80 for colour scale rated average and minimum SWV.ConclusionsThis is the first reported study of SW-EUS in synovial tissue. Maximum SWV was significantly lower in the synovium of RA patients compared with controls. There was a negative correlation between maximum SWV and GSUS graded synovial thickening suggesting that SWV may be lower in more active patients. SW-EUS may have a role in the diagnosis and assessment of disease activity in RA.Disclosure of InterestNone declared