title: Toronto alexithymia scale for patients with eating disorder: [corrected] performance using the non-parametric item response theory.
abstract: BACKGROUND
  The aim of this study was to investigate the performance of the Toronto Alexithymia Scale (TAS-20) in patients with eating disorders. As a secondary objective, we analyzed a subset of items in order to determine whether the total score is a good tool for classifying these patients and whether the items are ordered according to the difficulty of choosing a particular answer depending on the severity of the patient's condition.
  
  
  METHODS
  We administered the TAS-20 to 103 consecutive patients who met DSM-IV-R criteria for anorexia nervosa, bulimia nervosa, or eating disorders not otherwise specified. Mokken scale analysis, nonparametric item response theory (NIRT), and confirmatory factor analysis (CFA) were used to test the psychometric properties of the scale. To improve our understanding of the structure underlying the TAS-20, we used an automated item selection procedure based on the Mokken scale.
  
  
  RESULTS
  We identified a subset of 13 independent and clinically interpretable items that are potentially sufficient to rate patients with alexithymia. This subset was considered a unidimensional reduction of the TAS-20. However, the scale composed of this subset needs to be validated. Thirteen of the 20 items were maximally related to alexithymia because they have a one-dimensional structure. The NIRT and CFA enabled us to identify a maximal subset of items that conform to the requirements for good measurement of alexithymia in patients with eating disorders.
authors.affiliation: Department of Neurosciences, Psychiatry, Medical School, University of the Basque Country UPV/EHU, Spain; Bizkaia Mental Health Network (RSMB), Basque Health Service-Osakidetza, Spain.
authors.forename: Virginia
authors.initials: V
authors.lastname: Guillén
authors.affiliation: Department of Neurosciences, Psychiatry, Medical School, University of the Basque Country UPV/EHU, Spain.
authors.forename: Borja
authors.initials: B
authors.lastname: Santos
authors.affiliation: Bizkaia Mental Health Network (RSMB), Basque Health Service-Osakidetza, Spain.
authors.forename: Pedro
authors.initials: P
authors.lastname: Muñoz
authors.affiliation: Psychiatry Service, Santiago Apóstol Hospital, Basque Health Service-Osakidetza, Spain; Biomedical Research Centre in Mental Health (CIBERSAM), Group G10, Spain.
authors.forename: Blanca
authors.initials: B
authors.lastname: Fernández de Corres
authors.affiliation: Psychiatry Service, Santiago Apóstol Hospital, Basque Health Service-Osakidetza, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Fernández
authors.affiliation: Psychiatry Service, Santiago Apóstol Hospital, Basque Health Service-Osakidetza, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Pérez
authors.affiliation: Department of Neurosciences, Psychiatry, Medical School, University of the Basque Country UPV/EHU, Spain; Psychiatry Service, Santiago Apóstol Hospital, Basque Health Service-Osakidetza, Spain; Biomedical Research Centre in Mental Health (CIBERSAM), Group G10, Spain. Electronic address: anamaria.gonzalez-pintoarrillaga@osakidetza.net.
authors.forename: Ana Ma
authors.initials: AM
authors.lastname: González-Pinto
authors.affiliation: Department of Neurosciences, Psychiatry, Medical School, University of the Basque Country UPV/EHU, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Yllá
authors.affiliation: Department of Neurosciences, Psychiatry, Medical School, University of the Basque Country UPV/EHU, Spain; Biomedical Research Centre in Mental Health (CIBERSAM), Group G10, Spain.
authors.forename: Asunción
authors.initials: A
authors.lastname: González-Pinto
mesh_terms: D000293:Adolescent; D000328:Adult; D000342:Affective Symptoms / Q000175:diagnosis* / Q000523:psychology; D000856:Anorexia Nervosa / Q000175:diagnosis* / Q000523:psychology; D052018:Bulimia Nervosa / Q000175:diagnosis* / Q000523:psychology; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D011569:Psychiatric Status Rating Scales; D011594:Psychometrics / Q000379:methods; D055815:Young Adult