title: Validation of the Turkish version of the Celiac Disease Questionnaire (CDQ).
abstract: BACKGROUND
  The aim of the study was to translate, adapt and validate the Celiac Disease Questionnaire (CDQ), which was developed in Germany, for use in Turkey.
  
  
  METHODS
  The questionnaire was translated by a forward-backward translation method. Total CDQ score and four subscores (emotional state, gastrointestinal symptoms, worries, social problems) were calculated and their reliability assessed by internal consistency. Reliability of scales was evaluated by internal consistency. Test-retest reliability was assessed by means of a retest after 15 days. Face validity was assessed by patient volunteers and physicians and construct validity was assessed by means of confirmatory factor analysis. Convergent validity was determined by comparing responses to the CDQ with similar subscale scores of the Short Form-36 (SF-36) health survey. Discriminative concurrent criterion validity was determined by comparing the CDQ scores of patients with celiac disease (CD) on a gluten-free diet (GFD) with CD patients not on a GFD.
  
  
  RESULTS
  The Turkish version of the CDQ was completed by 205 patients with celiac disease (Female 146, mean age 31.1 year, ± 10.61). The Cronbach-α coefficent of the subscores ranged between 0.73 and 0.93. Test-retest reliability was 0.99 for all subscores. 42 patients with CD and five gastroenterologists assessed the items of the CDQ to be comprehensible and relevant to the health related quality of life (HRQOL) of CD patients. The confirmatory factor analysis demonstrated acceptable fit indices for the original four subscales of the CDQ. The correlations between the scales of the CDQ and the instrument for validation covering similar dimensions of the HRQOL ranged between 0.61 and 0.93. In all subscores and in the total score, patients not on a GFD showed a significantly reduced HRQOL (all p < 0.05) compared to patients on a GFD.
  
  
  CONCLUSIONS
  The Turkish version of the CDQ proved to be a reliable and valid instrument for measuring HRQOL in Turkish patients with celiac disease.
authors.affiliation: Department of Nutrition and Dietetics, Hacettepe University Faculty of Health Sciences, 06100, Ankara, Turkey. aysegul.cakmak@hacettepe.edu.tr.
authors.forename: Ayşegül
authors.initials: A
authors.lastname: Aksan
authors.affiliation: Department of Nutrition and Dietetics, Hacettepe University Faculty of Health Sciences, 06100, Ankara, Turkey.|Department of Nutrition and Dietetics, Eastern Mediterranean University Faculty of Health Sciences, via Mersin 10, Famagusta, T.R. North Cyprus, Turkey.
authors.forename: Seyit Mehmet
authors.initials: SM
authors.lastname: Mercanlıgil
authors.affiliation: Department of Psychosomatic Medicine and Psychotherapy, Technische Universität München, D-81865, Munich, Germany.
authors.forename: Winfried
authors.initials: W
authors.lastname: Häuser
authors.affiliation: Biostatistics Department, Hacettepe University Faculty of Medicine , 06100, Ankara, Turkey.
authors.forename: Eda
authors.initials: E
authors.lastname: Karaismailoğlu
mesh_terms: D000328:Adult; D000368:Aged; D002446:Celiac Disease / Q000523:psychology* / Q000628:therapy; D055050:Diet, Gluten-Free / Q000523:psychology*; D004644:Emotions; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D011594:Psychometrics; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards*; D014177:Translations; D014421:Turkey; D055815:Young Adult