One-year Followup Study on Clinical Findings and Changes in Magnetic Resonance Imaging-based Disease Activity Scores in Juvenile Idiopathic Arthritis

Objective. To evaluate whether clinical disease activity findings during 1-year followup of patients with juvenile idiopathic arthritis (JIA) is associated with changes of magnetic resonance imaging (MRI)-based disease activity scores. Methods. Patients with JIA who had active knee involvement were studied using an open-bore MRI. After followup of a median of 1.3 years, patients were re-evaluated and classified as improved or unimproved according to the American College of Rheumatology Pediatric-50 (ACR-Ped50) criteria. Baseline and followup MRI features were scored by 2 readers using the Juvenile Arthritis MRI Scoring (JAMRIS) system, comprising validated scores for synovial hypertrophy, bone marrow changes, cartilage lesions, and bone erosions. Results. Data of 40 patients were analyzed (62.5% female, mean age 12.2 yrs). After followup, 27 patients (67.5%) were classified as clinically improved, whereas 13 patients (32.5%) showed no clinical improvement. The clinically improved patients showed a significant reduction in synovial hypertrophy scores during followup (p < 0.001), with substantial effects (standardized response mean -0.70). No such changes were observed for any of the other MRI features. Significant differences were detected regarding a change in synovial hypertrophy scores comparing clinically improved and unimproved patients (p = 0.004), without statistically significant differences for changes in scores for bone marrow changes (p = 0.079), cartilage lesions (p = 0.165), and bone erosions (p = 0.078). Conclusion. This is one of the first studies to provide evidence for MRI-based improvement upon followup in JIA patients with knee involvement. There is a strong association with clinical improvement according to the ACR-Ped50 criteria and changes in MRI-based synovial hypertrophy scores, supporting the role of MRI as a responsive outcome measure to evaluate disease activity with antiinflammatory treatment strategies.