The Development and Validation of Quantitative Imaging Biomarkers as a Measure of Disease Activity in Juvenile Idiopathic Arthritis

This body of research will comprise a number of sub-studies, each designed to evaluate the use of quantitative MRI in JIA. Although patients will receive treatment during the study, this will form part of their routine clinical care and therefore this study is best regarded as observational.

1. Subjects and recruitment

Patients will be recruited by clinical rheumatologists working in a specialist adolescent and young adult inflammatory arthritis tertiary referral centre, on a person-to-person basis. Patients will be aged 12-24 and have a diagnosis of JIA according to established clinical criteria.8,9 Individuals with enthesitis-related arthropathy and those with other forms of JIA (extended oligorticular and polyarthritis (rheumatoid factor positive and negative)) will be divided into separate groups and asked to have an MRI scan. Control subjects will be recruited from the same clinic, and will consist of individuals with mechanical back pain (non-inflammatory - thought to arise from vertebrae, discs or ligaments) and normal inflammatory markers. Such patients still require an MRI scan as part of their routine care to confirm the mechanical cause for their back pain and definitively rule out inflammation as a cause, but serve as non-inflammatory controls. All patients will be asked to provide written consent at the time of enrolment.

Patients will include both patients with a new diagnosis of JIA and those with established disease who are already on treatment. For obvious ethical reasons, patients will not be divided into different treatment groups. 2. Study Design

Patients will be divided according to diagnostic group - group A will consist of patients with ERA (and also controls who are subsequently diagnosed with mechanical back pain), while group B will consist of patients with ERA, extended oligo- and polyarthritis. As detailed below, the scan protocol will be different for these two groups. JIA patients in both groups will be scanned at enrolment and will have repeat scans every 6-12 months, depending on clinical need, for up to five years in total. Thereafter, scans will be performed as defined by the requirements of their clinical care up to year 10 of study. The control group in group A will only be scanned once. They will be asked to provide written consent prior to enrolling. The imaging component of the study will run for up to five years in total, and approximately 200 patients will be recruited in total.