title: Extensive validation of the pain disability index in 3 groups of patients with musculoskeletal pain.
abstract: METHODS
  A cross-sectional study design was performed.
  
  
  OBJECTIVE
  To validate the pain disability index (PDI) extensively in 3 groups of patients with musculoskeletal pain.
  
  
  BACKGROUND
  The PDI is a widely used and studied instrument for disability related to various pain syndromes, although there is conflicting evidence concerning factor structure, test-retest reliability, and missing items. Additionally, an official translation of the Dutch language version has never been performed.
  
  
  METHODS
  For reliability, internal consistency, factor structure, test-retest reliability and measurement error were calculated. Validity was tested with hypothesized correlations with pain intensity, kinesiophobia, Rand-36 subscales, Depression, Roland-Morris Disability Questionnaire, Quality of Life, and Work Status. Structural validity was tested with independent backward translation and approval from the original authors.
  
  
  RESULTS
  One hundred seventy-eight patients with acute back pain, 425 patients with chronic low back pain and 365 with widespread pain were included. Internal consistency of the PDI was good. One factor was identified with factor analyses. Test-retest reliability was good for the PDI (intraclass correlation coefficient, 0.76). Standard error of measurement was 6.5 points and smallest detectable change was 17.9 points. Little correlations between the PDI were observed with kinesiophobia and depression, fair correlations with pain intensity, work status, and vitality and moderate correlations with the Rand-36 subscales and the Roland-Morris Disability Questionnaire.
  
  
  CONCLUSIONS
  The PDI-Dutch language version is internally consistent as a 1-factor structure, and test-retest reliable. Missing items seem high in sexual and professional items. Using the PDI as a 2-factor questionnaire has no additional value and is unreliable.
authors: *Groningen Spine Center, University of Groningen, University Medical Center Groningen, the Netherlands †Center for Rehabilitation; University of Groningen, University Medical Center Groningen, the Netherlands ‡Department of Rehabilitation Medicine; Research School of CAPHRI, Maastricht University, the Netherlands §Department of Neurology ¶Department of Neurosurgery, and ‖Department of Rehabilitation Medicine, University of Groningen, University Medical Center Groningen, the Netherlands; and **Adelante Centre of Expertise in Rehabilitation and Audiology, Hoensbroek, the Netherlands.
authors: Remko
authors: R
authors: Soer
authors: Albère J A
authors: AJ
authors: Köke
authors: Patrick C A J
authors: PC
authors: Vroomen
authors: Patrick
authors: P
authors: Stegeman
authors: Rob J E M
authors: RJ
authors: Smeets
authors: Maarten H
authors: MH
authors: Coppes
authors: Michiel F
authors: MF
authors: Reneman
mesh_terms: D000328:Adult; D000368:Aged; D003431:Cross-Cultural Comparison; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D059352:Musculoskeletal Pain / Q000175:diagnosis* / Q000208:ethnology*; D010147:Pain Measurement / Q000592:standards*