Material and Methods: We included a cohort of patients with newly diagnosed RA. The wrist and finger joints of the same hand; 2., 3., 4. metacarpophalangeal (MCP); and 2., 3., 4. proximal interphalangeal (PIP) joints were evaluated using both US and MRI. US evaluated active synovitis, the power Doppler (PD) signal, bone erosion, and tenosynovitis in joints. Clinical examination and the erythrocyte sedimentation rate and C-reactive protein level were simultaneously evaluated.

Results: We enrolled 31 patients with newly diagnosed RA and included 279 joints in the study. Radiocarpal synovitis was detected more frequently than midcarpal and ulnocarpal joint synovitis in the wrist joints. The sensitivity, specificity, and accuracy of US in detecting PD synovitis in wrist joints were 0.73, 0.76, and 0.74, respectively, compared with MRI. Both PDUS and gray-scale US had lower sensitivity, specificity, and accuracy in detecting synovitis and erosions in finger joints compared with MRI. PD synovitis total scores were highly correlated with disease duration, morning stiffness, and hand grip strength (r=0.448, p=0.032; r=0.500, p<0.001; r=0.843, p<0.001).

Conclusion: We demonstrated that the efficacy of US is comparable with that of contrast-enhanced MRI in detecting arthritis. However, clinicians must be careful so as to not obtain misleading information regarding MCP and PIP joints using US in patients with synovitis and erosions. Keywords : Rheumatoid arthritis, ultrasonography, magnetic resonance imaging, inflammation