Ultrasound (US) is sensitive for detecting joint and tendon inflammation in patients with rheumatoid arthritis (RA). So far, which grade of abnormalities on US corresponds to clinical manifestations is unclear. This study aimed to investigate the agreement between US-detected joint inflammation and clinical signs (joint swelling and tenderness).
In this cross-sectional study, 22 joints of the wrists and hands were, respectively, evaluated by physical examination (PE) and ultrasound in RA patients. Gray scale (GS) and power Doppler (PD) of synovitis, detected by ultrasound, were graded by semi-quantitative scoring systems (0-3). Tenosynovitis and peritendinitis were assessed qualitatively (0/1).
A total of 258 consecutive RA patients were included, with median disease duration of 57 months and mean Disease Activity Score based on 28 joints (DAS28)-ESR/DAS28-CRP of 4.47/3.99. In a total of 5676 joints assessed, the overall concordance rate between positive clinical signs and ultrasound-determined joint inflammation was fair (κ = 0.365, p < 0.01). In wrists, joint tenderness showed higher κ coefficient (κ = 0.329, p < 0.01) with ultrasound-determined joint inflammation than swelling (κ = 0.263, p < 0.01); however, swelling showed higher κ coefficient (κ = 0.156-0.536, p < 0.01) with ultrasound-determined joint inflammation than tenderness (κ = 0.061-0.355, p < 0.01) in metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints. Synovitis had consistently higher agreement with tenderness and swelling than tenosynovitis/peritendinitis. Tenderness and swelling had the highest κ coefficient with GS ≥ 1 synovial hyperplasia in most MCP and PIP joints, while with GS ≥ 2 synovial hyperplasia in wrists. For all 22 joints, PD ≥ 1 synovitis had the highest κ coefficient with clinical tenderness and swelling.
Synovitis had better agreement with clinical signs than tenosynovitis/peritendinitis. Joint swelling showed better agreement with US-determined inflammation than tenderness for MCP and PIP joints, while the opposite for wrists. Both tenderness and swelling are more likely to correspond to GS ≥ 2 for wrists, GS ≥ 1 for MCP and PIP joints, and PD ≥ 1 for any joint.