Background Magnetic Resonance Imaging (MRI) is increasingly used to measure disease activity in Rheumatoid Arthritis (RA) patients for research purposes. A main advantage of MRI is that it measures inflammation of the synovium of the joint, synovium of the tendons (tenosynovitis) and of the bone (bone marrow edema). The exact role of MRI in research as well as in daily practice in this patient group is not clear yet.
Objectives An important issue, not yet addressed, is to understand to what extend inflammatory abnormalities on MRI are in concordance to abnormalities at physical examination of joints. We performed the present study to determine this.
Methods 179 early arthritis patients included in the Leiden Early Arthritis Clinic underwent at the first visit a 68-tender and 66-swollen joint count (including MCP, wrist and MTP joints) and a 1.5T MRI of the MCP (2-4), wrist and MTP (1-5) joints at the most painful or dominant side. Synovitis and bone marrow edema were scored according to the RAMRIS method and in addition the presence of tenosynovitis at the wrists and MCP joints was determined. The MR images were scored by two readers and the average scores studied. The MRI data were dichotomized (cut-off ≥1) to compare concordance of the assessment of inflammation using MRI and physical examination.
Results 1,790 small joints of 179 patients were studied. Of these joints; 15% of the MCP joints, 30% of the wrists and 11% of the MTP joints were swollen at physical examination. The prevalence of a score ≥1 synovitis, bone marrow edema and tenosynovitis on MRI in MCP joints was; 26%, 17% and 21%; in wrists 60%, 58% and 52% and in MTP joints 7% and 12%, respectively.
In swollen MCP joints any inflammation was present in 86% (synovitis was present in 73%, bone marrow edema in 50% and tenosynovitis in 65%). Similarly, in swollen wrists any inflammation was present in 92% (83%, 75%, 78%, for the individual features respectively).
In clinically not swollen MCP joints any inflammation was present in 27% (synovitis was present in 18%, bone marrow edema in 10% and tenosynovitis in 13%). In not swollen wrists, any inflammation was present in 66% (50%, 51%, 41%, for the individual features respectively). In not swollen MTP joints any sign of inflammation was observed in 13% (5% for synovitis and 11% for bone marrow edema).
When evaluating all joints with any bone marrow edema, clinical joint swelling was absent in 53% of the MCP joints, 60% of the wrists and 78% of the MTP joints. When evaluating the joints with severe bone marrow edema (score ≥3), joint swelling was absent in 39% of the MCP joints, 35% of the wrists and 58% of the MTP joints.
Similar analyses were done for joint tenderness and in the subgroup of early arthritis patients fulfilling the 2010-criteria for RA (n= 65); these analyses yielded comparable results.
Conclusions This study shows that inflammation on MRI is present in a high percentage of the clinically swollen joints, but also in part of the non swollen joints. Moreover, a great majority of bone marrow edema lesions occur in clinically non swollen joints. The relevance of this subclinical inflammation with regards to the course of the disease is subject for further studies.
Disclosure of Interest None Declared