Living with arthritis severely affects a child’s ability to enjoy regular activities with friends and family and participate in school. Recently, effective drugs called “biologics” have become available for children with arthritis. They are expensive, however, causing a burden on public and private health care systems. In this project, they will allow doctors and families to quickly know: 1) who needs biologics, 2) which biologic works best for the individual child, and 3) when can the biologic be safely stopped. Our research team will develop the first genomics-based, low-cost biomarker blood tests to rapidly identify the best treatment for each individual child, completely transforming the care of childhood arthritis. Project outcomes are expected to have immediate impact on treatment and quality of life for children with arthritis.