title: Rasch analysis of the hospital anxiety and depression scale (HADS) for use in motor neurone disease.
abstract: BACKGROUND
  The Hospital Anxiety and Depression Scale (HADS) is commonly used to assess symptoms of anxiety and depression in motor neurone disease (MND). The measure has never been specifically validated for use within this population, despite questions raised about the scale's validity. This study seeks to analyse the construct validity of the HADS in MND by fitting its data to the Rasch model.
  
  
  METHODS
  The scale was administered to 298 patients with MND. Scale assessment included model fit, differential item functioning (DIF), unidimensionality, local dependency and category threshold analysis.
  
  
  RESULTS
  Rasch analyses were carried out on the HADS total score as well as depression and anxiety subscales (HADS-T, D and A respectively). After removing one item from both of the seven item scales, it was possible to produce modified HADS-A and HADS-D scales which fit the Rasch model. An 11-item higher-order HADS-T total scale was found to fit the Rasch model following the removal of one further item.
  
  
  CONCLUSIONS
  Our results suggest that a modified HADS-A and HADS-D are unidimensional, free of DIF and have good fit to the Rasch model in this population. As such they are suitable for use in MND clinics or research. The use of the modified HADS-T as a higher-order measure of psychological distress was supported by our data. Revised cut-off points are given for the modified HADS-A and HADS-D subscales.
authors.affiliation: Walton Centre for Neurology and Neurosurgery, Lower Lane, Liverpool, UK. chrisg@liv.ac.uk
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Gibbons
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Mills
authors.forename: Everard W
authors.initials: EW
authors.lastname: Thornton
authors.forename: John
authors.initials: J
authors.lastname: Ealing
authors.forename: John D
authors.initials: JD
authors.lastname: Mitchell
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Shaw
authors.forename: Kevin
authors.initials: K
authors.lastname: Talbot
authors.forename: Alan
authors.initials: A
authors.lastname: Tennant
authors.forename: Carolyn A
authors.initials: CA
authors.lastname: Young
mesh_terms: D001008:Anxiety Disorders / Q000175:diagnosis* / Q000209:etiology / Q000523:psychology; D016009:Chi-Square Distribution; D003866:Depressive Disorder / Q000175:diagnosis* / Q000209:etiology / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016472:Motor Neuron Disease / Q000150:complications* / Q000523:psychology*; D011569:Psychiatric Status Rating Scales; D011594:Psychometrics; D011795:Surveys and Questionnaires