title: How common is clinically inactive disease in a prospective cohort of patients with juvenile idiopathic arthritis? The importance of definition.
abstract: OBJECTIVE
  Many criteria for clinically inactive disease (CID) and minimal disease activity (MDA) have been proposed for juvenile idiopathic arthritis (JIA). It is not known to what degree each of these criteria overlap within a single patient cohort. This study aimed to compare the frequency of MDA and CID across different criteria in a cohort of children with JIA at 1 year following presentation.
  
  
  METHODS
  The Childhood Arthritis Prospective Study recruits children at initial presentation to paediatric or adolescent rheumatology in seven UK centres. Children recruited between October 2001 and December 2013 were included. The proportions of children with CID and MDA at 1 year were calculated using four investigator-defined and eight published composite criteria. Missing data were accounted for using multiple imputation under different assumptions.
  
  
  RESULTS
  In a cohort of 1415 children and adolescents, 67% patients had no active joints at 1 year. Between 48% and 61% achieved MDA and between 25% and 38% achieved CID using published criteria. Overlap between criteria varied. Of 922 patients in MDA by either the original composite criteria, Juvenile Arthritis Disease Activity Score (JADAS) or clinical JADAS cut-offs, 68% were classified as in MDA by all 3 criteria. Similarly, 44% of 633 children with CID defined by either Wallace's preliminary criteria or the JADAS cut-off were in CID according to both criteria.
  
  
  CONCLUSIONS
  In a large JIA prospective inception cohort, a majority of patients have evidence of persistent disease activity after 1 year. Published criteria to capture MDA and CID do not always identify the same groups of patients. This has significant implications when defining and applying treat-to-target strategies.
authors.affiliation: Arthritis Research UK Centre for Epidemiology, Division of Musculoskeletal and Dermatological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.|NIHR Manchester Musculoskeletal Biomedical Research Unit, Central Manchester University Hospitals NHS Foundation Trust and University of Manchester Partnership, Manchester, UK.
authors.forename: Stephanie J W
authors.initials: SJW
authors.lastname: Shoop-Worrall
authors.affiliation: Arthritis Research UK Centre for Epidemiology, Division of Musculoskeletal and Dermatological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.
authors.forename: Suzanne M M
authors.initials: SMM
authors.lastname: Verstappen
authors.affiliation: Paediatric Rheumatology, Alder Hey Children's NHS Foundation Trust, Liverpool, UK.
authors.forename: Eileen
authors.initials: E
authors.lastname: Baildam
authors.affiliation: Royal Manchester Children's Hospital, Manchester, UK.
authors.forename: Alice
authors.initials: A
authors.lastname: Chieng
authors.affiliation: The Royal Hospital for Children, Glasgow, UK.|The Royal Hospital for Sick Children, Edinburgh, UK.
authors.forename: Joyce
authors.initials: J
authors.lastname: Davidson
authors.affiliation: Great North Children's Hospital, Newcastle Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK.|Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Foster
authors.affiliation: Arthritis Research UK Centre for Adolescent Rheumatology, GOS Institute of Child Health, University College London, London, UK.
authors.forename: Yiannis
authors.initials: Y
authors.lastname: Ioannou
authors.affiliation: Great North Children's Hospital, Newcastle Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK.
authors.forename: Flora
authors.initials: F
authors.lastname: McErlane
authors.affiliation: Arthritis Research UK Centre for Adolescent Rheumatology, GOS Institute of Child Health, University College London, London, UK.|Paediatric Rheumatology, Great Ormond Street Hospital NHS Foundation Trust, London, UK.
authors.forename: Lucy R
authors.initials: LR
authors.lastname: Wedderburn
authors.affiliation: NIHR Manchester Musculoskeletal Biomedical Research Unit, Central Manchester University Hospitals NHS Foundation Trust and University of Manchester Partnership, Manchester, UK.|Arthritis Research UK Centre for Genetics and Genomics, The University of Manchester, Manchester, UK.
authors.forename: Wendy
authors.initials: W
authors.lastname: Thomson
authors.affiliation: Arthritis Research UK Centre for Epidemiology, Division of Musculoskeletal and Dermatological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.|NIHR Manchester Musculoskeletal Biomedical Research Unit, Central Manchester University Hospitals NHS Foundation Trust and University of Manchester Partnership, Manchester, UK.
authors.forename: Kimme L
authors.identifier: http://orcid.org/0000-0001-8242-9262
authors.initials: KL
authors.lastname: Hyrich
mesh_terms: D000293:Adolescent; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001171:Arthritis, Juvenile / Q000145:classification / Q000188:drug therapy / Q000276:immunology / Q000503:physiopathology*; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000276:immunology; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D012217:Rheumatoid Factor / Q000276:immunology; D012720:Severity of Illness Index; D006113:United Kingdom
chemical_list: D018501:Antirheumatic Agents; D002097:C-Reactive Protein; D012217:Rheumatoid Factor
keywords: Disease Activity; Juvenile Idiopathic Arthritis; Outcomes research