Magnetic Resonance Imaging (MRI) of the Knee as an Outcome Measure in Juvenile Idiopathic Arthritis: An OMERACT Reliability Study on MRI Scales.

OBJECTIVE: There is increasing evidence that early therapeutic intervention improves longterm joint outcome in juvenile idiopathic arthritis (JIA). Given the existence of highly effective treatments, there is an urgent need for reliable and accurate measures of disease activity and joint damage in JIA. Our objective was to assess the reliability of 2 magnetic resonance imaging (MRI) scoring methods: the Juvenile Arthritis MRI Scoring (JAMRIS) system and the International Prophylaxis Study Group (IPSG) consensus score, for evaluating disease status of the knee in patients with JIA.

METHODS: Four international readers independently scored an MRI dataset of 25 JIA patients with clinical knee involvement. Synovial thickening, joint effusion, bone marrow changes, cartilage lesions, bone erosions, and subchondral cysts were scored using the JAMRIS and IPSG systems. Further, synovial enhancement, infrapatellar fat pad heterogeneity, tendinopathy, and enthesopathy were scored. Interreader reliability was analyzed by using the generalized κ, ICC, and the smallest detectable difference (SDD).

RESULTS: ICC regarding interreader reliability ranged from 0.33 (95% CI 0.12-0.52, SDD = 0.29) for enthesopathy up to 0.95 (95% CI 0.92-0.97, SDD = 3.19) for synovial thickening. Good interreader reliability was found concerning joint effusion (ICC 0.93, 95% CI 0.89-0.95, SDD = 0.51), synovial enhancement (ICC 0.90, 95% CI 0.85-0.94, SDD = 9.85), and bone marrow changes (ICC 0.87, 95% CI 0.80-0.92, SDD = 10.94). Moderate to substantial reliability was found concerning cartilage lesions and bone erosions (ICC 0.55-0.72, SDD 1.41-13.65).

CONCLUSION: The preliminary results are promising for most of the scored JAMRIS and IPSG items. However, further refinement of the scoring system is warranted for unsatisfactorily reliable items such as bone erosions, cartilage lesions, and enthesopathy.