title: Comparing different revisions of the Childhood Health Assessment Questionnaire to reduce the ceiling effect and improve score distribution: Data from a multi-center European cohort study of children with JIA.
abstract: BACKGROUND
  The original version of the Childhood Health Assessment Questionnaire (CHAQ30orig) suffers from a ceiling effect and hence has reduced clinical validity. The purpose of this study was to evaluate the effect of adding eight more demanding items (CHAQ38) and a new categorical response option (CATII) on discriminant validity and score distribution in a European patient sample.
  
  
  METHODS
  Eighty-nine children with Juvenile Idiopathic arthritis (JIA) and 22 healthy controls, aged 7-16 years, were recruited from eight centres across Europe. Eight new CHAQ items and scoring option were translated back and forth for the countries in which they were not already present. Demographic, clinical, and CHAQ data were collected on-site. Subsequently, five different scoring methods were applied, i.e. the original method (CHAQ30orig) and four alternatives. These alternatives consisted of the mean item scores for the 30 and 38-question versions with either the original (CATI), or the new categorical response option (CATII). The five versions were tested for their ability to distinguish between patients and controls. Furthermore score distributions were evaluated and visualized by box and whisker plots.
  
  
  RESULTS
  Two CHAQ revisions with the new response option showed poor discriminative ability, whereas one revised version (CHAQ38CATI) had comparable discriminative ability comparable to the original CHAQ. A profound ceiling effect was observed in the original scoring method of the CHAQ (27%). The addition of eight more demanding items and application of a plain mean item score reduced this significantly to 14% (chi2 = 4.21; p < 0.05).
  
  
  CONCLUSIONS
  Revising the CHAQ by adding eight more demanding items and applying a plain mean item scoring (CHAQ38CATI) maintained discriminant ability and reduced the ceiling effect in a European patient sample. The new categorical response option (CATII) seemed promising, but was less able to distinguish children with JIA from healthy controls and had less favourable distribution characteristics. The CHAQ38CATI is advocated for future use in mildly affected JIA patients.
authors.affiliation: Child Development and Exercise Centre, University Hospital for Children and Youth 'Het Wilhelmina Kinderziekenhuis' University Medical Centre Utrecht, Utrecht, the Netherlands. j.vandernet@umcutrecht.nl.
authors.forename: W
authors.initials: W
authors.lastname: Groen
authors.forename: E
authors.initials: E
authors.lastname: Unal
authors.forename: M
authors.initials: M
authors.lastname: Nørgaard
authors.forename: S
authors.initials: S
authors.lastname: Maillard
authors.forename: J
authors.initials: J
authors.lastname: Scott
authors.forename: K
authors.initials: K
authors.lastname: Berggren
authors.forename: E
authors.initials: E
authors.lastname: Sandstedt
authors.forename: M
authors.initials: M
authors.lastname: Stavrakidou
authors.forename: J
authors.initials: J
authors.lastname: van der Net