title: Item analysis using Rasch models confirms that the Danish versions of the DISABKIDS® chronic-generic and diabetes-specific modules are valid and reliable.
abstract: BACKGROUND
  Type 1 Diabetes (T1D) has a negative impact on psychological and overall well-being. Screening for Health-related Quality of Life (HrQoL) and addressing HrQoL issues in the clinic leads to improved well-being and metabolic outcomes. The aim of this study was to translate the generic and diabetes-specific validated multinational DISABKIDS® questionnaires into Danish, and then determine their validity and reliability.
  
  
  METHODS
  The questionnaires were translated using a validated translation procedure and completed by 99 children and adolescents from our diabetes-department; all diagnosed with T1D and were aged between 8 and 18 years old. The Rasch and the graphical log linear Rasch model (GLLRM) were used to determine validity. Monte Carlo methods and Cronbach's α were used to confirm reliability.
  
  
  RESULTS
  The data did not fit a pure Rasch model but did fit a GLLRM when item six in the independence scale is excluded. The six subscales measure different aspects of HrQoL indicating that all the subscales are necessary. The questionnaire shows local dependency between items and differential item functioning (DIF). Therefore age, gender, and glycated hemoglobin (HbA1c) levels must be taken into account when comparing HrQoL between groups.
  
  
  CONCLUSIONS
  The Danish versions of the DISABKIDS® chronic-generic and diabetes-specific modules provide valid and objective measurements with adequate reliability. These Danish versions are useful tools for evaluating HrQoL in Danish patients with T1D. However, guidelines on how to manage DIF and local independence will be required, and item six should be rephrased.
authors.affiliation: Copenhagen Diabetes Research Center (CPH-DIRECT), Department of Paediatrics, Herlev University Hospital, Herlev Ringvej 75, Herlev, 2730, Denmark. julie.bojstrup@gmail.com.
authors.forename: Julie Bøjstrup
authors.initials: JB
authors.lastname: Nielsen
authors.affiliation: Copenhagen Diabetes Research Center (CPH-DIRECT), Department of Paediatrics, Herlev University Hospital, Herlev Ringvej 75, Herlev, 2730, Denmark.
authors.forename: Julie Nyholm
authors.initials: JN
authors.lastname: Kyvsgaard
authors.affiliation: Copenhagen Diabetes Research Center (CPH-DIRECT), Department of Paediatrics, Herlev University Hospital, Herlev Ringvej 75, Herlev, 2730, Denmark.
authors.forename: Stine Møller
authors.initials: SM
authors.lastname: Sildorf
authors.affiliation: Section of Biostatistics, Department of Public Health, Faculty of Health and Medical Sciences, University of Copenhagen, Øster Farimagsgade 5, Copenhagen K, 1014, Denmark.
authors.forename: Svend
authors.initials: S
authors.lastname: Kreiner
authors.affiliation: Copenhagen Diabetes Research Center (CPH-DIRECT), Department of Paediatrics, Herlev University Hospital, Herlev Ringvej 75, Herlev, 2730, Denmark.
authors.forename: Jannet
authors.initials: J
authors.lastname: Svensson
mesh_terms: D000293:Adolescent; D002648:Child; D003718:Denmark; D003922:Diabetes Mellitus, Type 1 / Q000523:psychology*; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D011594:Psychometrics; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards*; D014175:Translating; D016896:Treatment Outcome
keywords: Adolescents; Children; Chronic condition; DISABKIDS; Diabetes type 1; HrQoL; Rasch