title: Rasch measurement properties of the KIDSCREEN quality of life instrument in children with cerebral palsy and differential item functioning between children with and without cerebral palsy.
abstract: OBJECTIVE
  To assess if the Rasch-scaled KIDSCREEN-52 generic health-related quality of life measure was valid in children with cerebral palsy (CP).
  
  
  METHODS
  The Rasch measurement properties and differential item functioning (DIF) of the KIDSCREEN-52 were examined in children with CP. Data were available from the KIDSCREEN project from 3219 children aged 8 to 12 years and 2126 parents in the general population; and from the SPARCLE project from 501 children aged 8 to 12 years with CP and 823 parents. Analysis used Zumbo's logistic regression DIF approach. Partial credit model analyses were conducted.
  
  
  RESULTS
  All items of the KIDSCREEN self-report version fitted the partial credit model (smallest P-value: 0.256). Only one item of the parent version did not fit the data well (smallest P-value 0.001). Statistically significant DIF was observed in some items, but was of substantial magnitude (ΔR2 = 0.046, 0.049) for only two items in two dimensions of the parent version. The practical impact of DIF was small. DIF-adjusted standardized mean differences between children with and without CP being 1.07 and 0.34 for the physical and school dimensions, respectively (unadjusted: 1.09 and 0.16).
  
  
  CONCLUSIONS
  The KIDSCREEN-52 functions in a similar way in children with CP and in the general population. Comparisons of quality of life between such children are therefore likely to be valid.
authors.affiliation: University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Erhart
authors.forename: Ulrike
authors.initials: U
authors.lastname: Ravens-Sieberer
authors.forename: Heather O
authors.initials: HO
authors.lastname: Dickinson
authors.forename: Allan
authors.initials: A
authors.lastname: Colver
mesh_terms: D000203:Activities of Daily Living / Q000523:psychology; D002547:Cerebral Palsy / Q000523:psychology*; D002648:Child; D005060:Europe; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires / Q000592:standards