title: Combination of classical test theory (CTT) and item response theory (IRT) analysis to study the psychometric properties of the French version of the Quality of Life Enjoyment and Satisfaction Questionnaire-Short Form (Q-LES-Q-SF).
abstract: OBJECTIVE
  The study aimed to examine the construct validity and reliability of the Quality of Life Enjoyment and Satisfaction Questionnaire-Short Form (Q-LES-Q-SF) according to both classical test and item response theories.
  
  
  METHODS
  The psychometric properties of the French version of this instrument were investigated in a cross-sectional, multicenter study. A total of 124 outpatients with a substance dependence diagnosis participated in the study. Psychometric evaluation included descriptive analysis, internal consistency, test-retest reliability, and validity. The dimensionality of the instrument was explored using a combination of the classical test, confirmatory factor analysis (CFA), and an item response theory analysis, the Person Separation Index (PSI), in a complementary manner.
  
  
  RESULTS
  The results of the Q-LES-Q-SF revealed that the questionnaire was easy to administer and the acceptability was good. The internal consistency and the test-retest reliability were 0.9 and 0.88, respectively. All items were significantly correlated with the total score and the SF-12 used in the study. The CFA with one factor model was good, and for the unidimensional construct, the PSI was found to be 0.902.
  
  
  CONCLUSIONS
  The French version of the Q-LES-Q-SF yielded valid and reliable clinical assessments of the quality of life for future research and clinical practice involving French substance abusers. In response to recent questioning regarding the unidimensionality or bidimensionality of the instrument and according to the underlying theoretical unidimensional construct used for its development, this study suggests the Q-LES-Q-SF as a one-dimension questionnaire in French QoL studies.
authors.affiliation: Service médico-psychologique régional, Metz, France, steph_bedes@yahoo.fr.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Bourion-Bédès
authors.forename: Raymund
authors.initials: R
authors.lastname: Schwan
authors.forename: Jonathan
authors.initials: J
authors.lastname: Epstein
authors.forename: Vincent
authors.initials: V
authors.lastname: Laprevote
authors.forename: Alex
authors.initials: A
authors.lastname: Bédès
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Bonnet
authors.forename: Cédric
authors.initials: C
authors.lastname: Baumann
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D005163:Factor Analysis, Statistical; D005260:Female; D005602:France; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D010549:Personal Satisfaction; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D019966:Substance-Related Disorders; D011795:Surveys and Questionnaires