The OMERACT Ultrasound Task Force is currently developing a global synovitis score (GLOSS) with the objective of feasibly measuring global disease activity in patients with rheumatoid arthritis (RA). In order to determine the minimal number of joints to be included in such a scoring system, and to analyze the metric properties of proposed global (i.e., patient level) ultrasound (US) scoring systems of synovitis in RA, a systematic analysis of the literature was performed.
A systematic literature search of Pubmed and Embase was performed (January 1, 1984, to March 31, 2010). Original research reports written in English including RA, ultrasound, Doppler, and scoring systems were included. The design, subjects, methods, imaging protocols, and performance characteristics studied were analyzed, as well as the ultrasound definition of synovitis.
Of 3004 reports identified, 14 articles were included in the review. We found a lack of clear definition of synovitis as well as varying validity data with respect to the proposed scores. Scoring systems included a wide range and number of joints. All analyzed studies assessed construct validity and responsiveness by using clinical examination, laboratory findings, and other imaging modalities as comparators. Both construct validity and responsiveness varied according to the number and size of joints examined and according to the component of synovitis measured [i.e., gray-scale (GS) or power Doppler (PD) alone or in combination]. With regard to feasibility, time of evaluation varied from 15 to 60 min and increased with the number of joints involved in the examination.
Ultrasound can be regarded as a valuable tool for globally examining the extent of synovitis in RA. However, it is presently difficult to determine a minimal number of joints to be included in a global ultrasound score. Further validation of proposed scores is needed.