title: CLARITY - ChiLdhood Arthritis Risk factor Identification sTudY.
abstract: BACKGROUND
  The aetiology of juvenile idiopathic arthritis (JIA) is largely unknown. We have established a JIA biobank in Melbourne, Australia called CLARITY - ChiLdhood Arthritis Risk factor Identification sTudY, with the broad aim of identifying genomic and environmental disease risk factors. We present here study protocols, and a comparison of socio-demographic, pregnancy, birth and early life characteristics of cases and controls collected over the first 3 years of the study.
  
  
  METHODS
  Cases are children aged ≤18 years with a diagnosis of JIA by 16 years. Controls are healthy children aged ≤18 years, born in the state of Victoria, undergoing a minor elective surgical procedure. Participant families provide clinical, epidemiological and environmental data via questionnaire, and a blood sample is collected.
  
  
  RESULTS
  Clinical characteristics of cases (n = 262) are similar to those previously reported. Demographically, cases were from families of higher socio-economic status. After taking this into account, the residual pregnancy and perinatal profiles of cases were similar to control children. No case-control differences in breastfeeding commencement or duration were detected, nor was there evidence of increased case exposure to tobacco smoke in utero. At interview, cases were less likely to be exposed to active parental smoking, but disease-related changes to parent behaviour may partly underlie this.
  
  
  CONCLUSIONS
  We show that, after taking into account socio-economic status, CLARITY cases and controls are well matched on basic epidemiological characteristics. CLARITY represents a new study platform with which to generate new knowledge as to the environmental and biological risk factors for JIA.
authors.affiliation: Genes, Environment and Complex Disease, Murdoch Childrens Research Institute, Parkville, VIC, Australia. justine.ellis@mcri.edu.au.
authors.forename: Justine A
authors.initials: JA
authors.lastname: Ellis
authors.forename: Anne-Louise
authors.initials: AL
authors.lastname: Ponsonby
authors.forename: Angela
authors.initials: A
authors.lastname: Pezic
authors.forename: Raul A
authors.initials: RA
authors.lastname: Chavez
authors.forename: Roger C
authors.initials: RC
authors.lastname: Allen
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Akikusa
authors.forename: Jane E
authors.initials: JE
authors.lastname: Munro