Reliability of Ultrasonography to Detect Synovitis in Rheumatoid Arthritis: A Systematic Literature Review of 35 Studies (1,415 Patients)

Objective. To perform a systematic review on the reliability of ultrasonographic (US) synovitis detection in rheumatoid arthritis (RA) by B-mode and power Doppler (PD) in image acquisition and still-image interpretation. US is a sensitive method for synovitis detection. However, reliability is still a key concern. Methods. Articles reporting any US reliability results for synovitis in RA in PubMed, EMBase, the Cochrane Library, and meeting abstracts were selected. Data were extracted from the collection of data on US synovitis detection (either qualitatively [binary] or semiquantitatively [0-3 scale], for intraobserver and interobserver reliability in B-mode and PD, and for image acquisition and still-image interpretation). The type of joints tested, the experience of the ultrasonographer, and the quality of the studies were assessed. Data analysis involved descriptive and graphic interpretation of reliability and its potential determinants. Results. Thirty-five studies (12 for B-mode, 11 for PD, or 12 for both) with a total of 1,415 patients were analyzed. Intraobserver and interobserver reliability for still images in B-mode and PD was high (kappa = 0.5-1.0 [14,991 joints] for intraobserver reliability for B-mode, kappa = 0.59-1.0 [14,934 joints] for PD, kappa = 0.49-1.0 [3,138 joints] for interobserver for B-mode, and kappa = 0.66-1.0 [3,325 joints] for PD). Interobserver reliability for image acquisition in both US modes was lower than still-image interpretation (kappa = 0.22-0.95). Few studies reported intraobserver image acquisition reliability. Conclusion. Intraobserver and interobserver reliability of still-image interpretation was high, especially for PD, in published studies involving highly trained observers. However, reliability of acquisition of US should be further assessed.