Predictors of persisting pain in children with Juvenile Idiopathic Arthritis: a case control study nested in the ReACCh-Out cohort oleh Tara McGrath, Jaime Guzman, Lori Tucker, Natalie J. Shiff, Maryna Yaskina, Susan Tupper, Dax G. Rumsey, for the Research in Arthritis in Canadian Children Emphasizing Outcomes (ReACCh-Out) Investigators