Patients considered to be treatment responders at week 24 according to the American College of Rheumatology ( ACR ) Pediatric 30 ( Pedi 30 ) criteria for improvement in juvenile arthritis entered the second phase , a 24-week randomized , double-blind , placebo-controlled withdrawal study , for an additional 24 weeks , for evaluation of the primary end point , occurrence of a disease flare from week 24 to week 48 , based on the ACR preliminary definition of disease flare in juvenile arthritis .