Reliability and responsiveness of the Juvenile Arthritis MRI Scoring (JAMRIS) system for the knee.

OBJECTIVES: To assess the reliability and responsiveness of a new Juvenile Arthritis MRI Scoring (JAMRIS) system for evaluating disease activity of the knee. METHODS: Twenty-five juvenile idiopathic arthritis (JIA) patients with clinical knee involvement were studied using open-bore 1-T MRI. MRI features of synovial hypertrophy, bone marrow changes, cartilage lesions and bone erosions were independently scored by five readers using the JAMRIS system. In addition, the JAMRIS system was determined to be a follow-up parameter by two readers to evaluate the response to therapy in 15 consecutive JIA patients. RESULTS: Inter-reader (ICCs 0.86-0.95) and intra-reader reliability (ICCs 0.92-1.00) for the scoring of JAMRIS features was good. Reliability of the actual scores and changes in scores over time was good for all items: ICCs 0.89-1.00, 0.87-1.00, respectively. Concerning therapy response, the mean synovial hypertrophy scores decreased significantly (mean 1.1 point; P < 0.001, SRM = -0.65). No change was observed with respect to bone marrow change, cartilage lesion and bone erosion scores. CONCLUSIONS: The JAMRIS proved to be a simple and highly reliable assessment score in the evaluation of JIA disease activity of the knee. The JAMRIS system may serve as an objective and accurate outcome measure in future research and clinical trials.