Use of magnetic resonance imaging in detecting subclinical synovitis in rheumatoid arthritis and correlation of imaging findings with interleukin-18 levels.

Aim: We studied the usefulness of magnetic resonance imaging (MRI) in detecting subclinical inflammation in patients with asymptomatic RA and tested the hypothesis of interleukin (IL)-18 as a marker of disease activity.

Methods: Thirteen RA patients with Disease Activity Score of 28 joints (DAS28) < 2.6 were evaluated. The patients underwent clinical evaluation, laboratory tests and MRI assessment. Imaging of bilateral hands and wrists was performed using validated acquisition and scoring techniques. Serum IL-18 levels were concurrently measured.

Results: MRI assessments showed that 92.3% and 76.9% of patients had synovitis and bone marrow edema, respectively, despite being in clinical remission. Eight out of 12 patients (66.7%) had erosions on MRI which were not visualised on plain radiographs. Of all the 182 joints studied for synovitis on MRI, only one had clinical evidence of joint swelling. Comparison of the total sum scores of synovitis between the right and left hand and wrist joints of individual patients showed a significant difference between the two sides. Measurements of IL-18 indicated that a large proportion (54%) of the patients had undetectable or very low levels of the cytokine.

Conclusion: MRI is more sensitive in detecting erosions compared with X-rays, and is superior in its ability to detect subclinical inflammation in RA patients. Despite being in clinical remission, a large majority of patients had imaging-detected synovitis and bone marrow edema. Our study highlights the usefulness of MRI for the accurate evaluation of disease activity. In the utility of MRI, it may be important to assess bilateral hands and wrists, instead of limiting to the dominant side.