title: Validation of the Dutch version of the Swallowing Quality-of-Life Questionnaire (DSWAL-QoL) and the adjusted DSWAL-QoL (aDSWAL-QoL) using item analysis with the Rasch model: a pilot study.
abstract: BACKGROUND
  The Swallowing Quality-of-Life Questionnaire (SWAL-QoL) is considered the gold standard for assessing health-related QoL in oropharyngeal dysphagia. The Dutch translation (DSWAL-QoL) and its adjusted version (aDSWAL-QoL) have been validated using classical test theory (CTT). However, these scales have not been tested against the Rasch measurement model, which is required to establish the structural validity and objectivity of the total scale and subscale scores. Thus, the purpose of this study was to examine the psychometric properties of these scales using item analysis according to the Rasch model.
  
  
  METHODS
  Item analysis with the Rasch model was performed using RUMM2030 software with previously collected data from a validation study of 108 patients. The assessment included evaluations of overall model fit, reliability, unidimensionality, threshold ordering, individual item and person fits, differential item functioning (DIF), local item dependency (LID) and targeting.
  
  
  RESULTS
  The analysis could not establish the psychometric properties of either of the scales or their subscales because they did not fit the Rasch model, and multidimensionality, disordered thresholds, DIF, and/or LID were found. The reliability and power of fit were high for the total scales (PSI = 0.93) but low for most of the subscales (PSI < 0.70). The targeting of persons and items was suboptimal. The main source of misfit was disordered thresholds for both the total scales and subscales. Based on the results of the analysis, adjustments to improve the scales were implemented as follows: disordered thresholds were rescaled, misfit items were removed and items were split for DIF. However, the multidimensionality and LID could not be resolved. The reliability and power of fit remained low for most of the subscales.
  
  
  CONCLUSIONS
  This study represents the first analyses of the DSWAL-QoL and aDSWAL-QoL with the Rasch model. Relying on the DSWAL-QoL and aDSWAL-QoL total and subscale scores to make conclusions regarding dysphagia-related HRQoL should be treated with caution before the structural validity and objectivity of both scales have been established. A larger and well-targeted sample is recommended to derive definitive conclusions about the items and scales. Solutions for the psychometric weaknesses suggested by the model and practical implications are discussed.
authors.affiliation: University of Antwerp, Antwerp, Belgium. ingeborg.simpelaere@vives.be.|VIVES University College, Bruges, Belgium. ingeborg.simpelaere@vives.be.|Department of Speech-Language Pathology, AZ Delta Hospital, Menen, Belgium. ingeborg.simpelaere@vives.be.
authors.forename: Ingeborg S
authors.initials: IS
authors.lastname: Simpelaere
authors.affiliation: Department of Otolaryngology and Rehabilitation Centre for Communication Disorders, Antwerp University Hospital, Antwerp, Belgium.|Department of Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium.|Department of Speech, Language and Hearing Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium.
authors.forename: Gwen
authors.initials: G
authors.lastname: Van Nuffelen
authors.affiliation: Department of Otolaryngology and Rehabilitation Centre for Communication Disorders, Antwerp University Hospital, Antwerp, Belgium.|Department of Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium.|Department of Speech, Language and Hearing Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium.
authors.forename: Marc
authors.initials: M
authors.lastname: De Bodt
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Saint-Pierre University Hospital, Brussels, Belgium.|Thomas More University College, Antwerp, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Vanderwegen
authors.affiliation: Institute of Physiotherapy and Occupational Therapy, Metropolitan University College, Copenhagen, Denmark.
authors.forename: Tina
authors.initials: T
authors.lastname: Hansen
mesh_terms: D000328:Adult; D000368:Aged; D001530:Belgium; D003679:Deglutition; D003680:Deglutition Disorders / Q000523:psychology* / Q000628:therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D010865:Pilot Projects; D011594:Psychometrics / Q000379:methods; D011788:Quality of Life; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards*; D014175:Translating; D055815:Young Adult
keywords: Deglutition disorders; Health-related quality of life; Oropharyngeal dysphagia; Outcome assessment; Psychometrics; Rasch model; SWAL-QoL