title: Factor structure of the Shoulder Pain and Disability Index in patients with adhesive capsulitis.
abstract: BACKGROUND
  The Shoulder Pain and Disability Index (SPADI) is a self-administered questionnaire that aims to measure pain and disability associated with shoulder disease. It consists of a pain section and a disability section with 13 items being responded to on visual analogue scales. Few researchers have investigated SPADI validity in specified diagnostic groups, although the selection of an evaluative instrument should be based on evidence of validity in the target patient group. The aim of the present study was to investigate factor structure of the SPADI in a study population of patients with adhesive capsulitis.
  
  
  METHODS
  The questionnaire was administered to 191 patients with adhesive capsulitis. Descriptive statistics for items and a comparison of scores for the two subscales were produced. Internal consistency was analyzed by use of the Cronbach alpha and a principal components analysis with varimax rotation was conducted. Study design was cross-sectional.
  
  
  RESULTS
  Two factors were extracted, but the factor structure failed to support the original division of items into separate pain and disability sections.
  
  
  CONCLUSIONS
  We found minimal evidence to justify the use of separate subscales for pain and disability. It is our impression that the SPADI should be viewed as essentially unidimensional in patients with adhesive capsulitis.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Ullevål University Hospital, University of Oslo, Oslo, Norway. e.k.tveita@medisin.uio.no
authors.forename: Einar Kristian
authors.initials: EK
authors.lastname: Tveitå
authors.forename: Leiv
authors.initials: L
authors.lastname: Sandvik
authors.forename: Ole Marius
authors.initials: OM
authors.lastname: Ekeberg
authors.forename: Niels Gunnar
authors.initials: NG
authors.lastname: Juel
authors.forename: Erik
authors.initials: E
authors.lastname: Bautz-Holter
mesh_terms: D002062:Bursitis / Q000175:diagnosis* / Q000503:physiopathology; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010045:Outpatients; D010147:Pain Measurement / Q000706:statistics & numerical data; D025341:Principal Component Analysis; D016059:Range of Motion, Articular; D012785:Shoulder Joint / Q000473:pathology* / Q000503:physiopathology; D020069:Shoulder Pain / Q000175:diagnosis* / Q000503:physiopathology; D011795:Surveys and Questionnaires