Synovitis and Osteitis Are Very Frequent in Rheumatoid Arthritis Clinical Remission: Results from an MRI Study of 294 Patients in Clinical Remission or Low Disease Activity State

Objective.In rheumatoid arthritis (RA), radiographic progression may occur despite clinical remission. This may be explained by subclinical inflammation. Magnetic resonance imaging (MRI) provides a greater sensitivity than clinical examination and radiography for assessing disease activity. Our objective was to determine the MRI characteristics of RA patients in clinical remission or low disease activity (LDA) state.Methods.Databases from 6 cohorts were collected from 5 international centers. RA patients in clinical remission according to Disease Activity Score28-C-reactive protein (DAS28-CRP < 2.6; n = 213) or LDA-state (2.6 ≤ DAS28-CRP < 3.2; n = 81) with available MRI data were included. MRI were assessed according to the OMERACT RA MRI scoring system (RAMRIS).Results.Patient characteristics: 70% women, median age 55 (interquartile range, IQR 43–63) years, disease duration 2.3 (IQR 0.7–5.1) years, DAS28-CRP 2.2 (IQR 1.8–2.6), Simplified Disease Activity Index, SDAI, 3.9 (IQR 1.9–6.5), Clinical Disease Activity Index, CDAI, 3.1 (IQR 1.5– 5.8), rheumatoid factor/anti-cyclic citrullinated peptide positivity 57%/54%, presence of radiographic erosions: 66%. Wrist and metacarpophalangeal MRI (MCP-MRI) data were available for 287 and 241 patients, respectively. MRI inflammatory activity in wrist and/or MCP joints was observed in the majority [synovitis: 95%, bone edema (osteitis): 35%] of patients. The median (IQR) RAMRIS score was 6 (3–9) for synovitis and 0 (0–2) for osteitis. Synovitis and osteitis were not less frequent in DAS28 clinical remission (synovitis/osteitis 96%/35%) than LDA (91/36). A trend towards lower frequencies of osteitis in patients in SDAI and CDAI remission was observed.Conclusion.Subclinical inflammation was identified by MRI in the majority of RA patients in clinical remission or LDA state. This may explain structural progression in such patients. Further work is required to understand the place of modern imaging in future remission criteria.