Scoring ultrasound synovitis in rheumatoid arthritis: a EULAR-OMERACT ultrasound taskforce - Part 1: definition and development of a standardised, consensus-based scoring system

Abstract

Objectives: To develop a consensus-based ultrasound (US) definition and quantification system for synovitis in rheumatoid arthritis (RA).

Methods: A multistep, iterative approach was used to: (1) evaluate the baseline agreement on defining and scoring synovitis according to the usual practice of different sonographers, using both grey-scale (GS) (synovial hypertrophy (SH) and effusion) and power Doppler (PD), by reading static images and scanning patients with RA and (2) evaluate the influence of both the definition and acquisition technique on reliability followed by a Delphi exercise to obtain consensus definitions for synovitis, elementary components and scoring system.

Results: Baseline reliability was highly variable but better for static than dynamic images that were directly acquired and immediately scored. Using static images, intrareader and inter-reader reliability for scoring PD were excellent for both binary and semiquantitative (SQ) grading but GS showed greater variability for both scoring systems (κ ranges: -0.05 to 1 and 0.59 to 0.92, respectively). In patient-based exercise, both intraobserver and interobserver reliability were variable and the mean κ coefficients did not reach 0.50 for any of the components. The second step resulted in refinement of the preliminary Outcome Measures in Rheumatology synovitis definition by including the presence of both hypoechoic SH and PD signal and the development of a SQ severity score, depending on both the amount of PD and the volume and appearance of SH.

Conclusion: A multistep consensus-based process has produced a standardised US definition and quantification system for RA synovitis including combined and individual SH and PD components. Further evaluation is required to understand its performance before application in clinical trials.

Keywords: EULAR; OMERACT; doppler; scoring system; synovitis; ultrasound.

Figure 1

(Panel 3a shows the schematic drawing of the individual grades of hypoechoic SH for GS alone. For each grade is also shown the corresponding GS image. (1) None=Grade 0: no SH independently of the presence of effusion; (2) minimal=Grade 1: SH with or without effusion up to level of horizontal line connecting bone surfaces M and P; (3) moderate=Grade 2: SH with or without effusion extending beyond joint line but with upper surface convex (curved downwards) or hypertrophy extending beyond joint line but with upper surface flat; (4) severe=Grade 3: SH with or without effusion extending beyond joint line but with upper surface flat or convex (curved downwards). Panel 2b shows the schematic drawing of the individual grades for Doppler activity. For each grade is also shown the corresponding ultrasound image. (1) None=Grade 0: no Doppler activity; (2) minimal=Grade 1: up to three single Doppler spots or up to one confluent spot and two single spots or up to two confluent spots; (3) moderate=Grade 2: greater than Grade 1 but <50% Doppler signals in the total GS background; (4) severe=Grade 3: greater than Grade 2 (>50% of the background GS). Panel 2c shows the EULAR-OMERACT score for PDUS synovitis combining grey-scale SH and PD signal. Normal joint=Grade 0: no grey-scale-detected SH and no PD signal (within the synovium); minimal synovitis=Grade 1: Grade 1 SH and ≤Grade 1 PD signal; moderate synovitis=Grade 2: Grade 2 SH and ≤Grade 2 PD signal or Grade 1 SH and a Grade 2 PD signal; severe synovitis=Grade 3: Grade 3 SH and ≤Grade 3 PD signal or Grade 1 or 2 synovial hypertrophy and a Grade 3 PD signal. fx1, connective tissue; EULAR, European League Against Rheumatism; GS, grey-scale; fx2, hypertrophy; fx3, joint line; fx4, loose intra-articular connective tissue; M, metacarpal head; P, proximal phalangeal bone; OMERACT, Outcome Measures in Rheumatology; PD, power Doppler; SH, synovial hypertrophy.