title: The conceptually equivalent Dutch version of the Western Ontario Rotator Cuff Index (WORC)©.
abstract: BACKGROUND
  The WORC is a quality of life questionnaire designed for patients with disorders of the rotator cuff, originally developed in English. The purpose of this study was to cross-culturally adapt the WORC for use in the Dutch population and to evaluate reliability, agreement and floor and ceiling effects of this Dutch version in a population of patients with rotator cuff disease.
  
  
  METHODS
  Reliability was tested by measuring the Cronbach's alpha for internal consistency and intraclass correlation coefficients (ICC) for test-retest reliability. Agreement was measured using the Standard Error of Measurement (SEM(agreement)); and the smallest detectable change (SDC) was calculated based on the SEM. Pearson Correlations Coefficients were used to comparing the WORC with the RAND-36, the Constant Score and 11-point shoulder hindrance scale.
  
  
  RESULTS
  Fifty-seven patients entered into this study of whom 50 were available for test-retest validation. The internal consistency of the Dutch WORC tested by Cronbach's alpha was 0.95 for the total questionnaire. The ICC for the WORC is 0.91 with a 95% confidence interval of 0.85-0.95. Standard Error of Measurement was 6.0 points with a Smallest Detectable Change of 16.7 points on a 0-100 scale. Pearson Correlations Coefficients showed a significant positive correlation between the Dutch WORC and Constant Score (r = 0.60) and a strong reversed correlation with the shoulder hindrance scale (r = -0.75).
  
  
  CONCLUSIONS
  The Dutch WORC seems to be a reliable health-related quality of life questionnaire for patients with rotator cuff disorders.
  
  
  BACKGROUND
  NCT01532492.
authors.affiliation: Department of Orthopaedic Surgery, St, Antonius Ziekenhuis, PO Box 2500, Nieuwegein 3430, EM, The Netherlands. r.wessel@antoniusziekenhuis.nl.
authors.forename: Ronald N
authors.initials: RN
authors.lastname: Wessel
authors.forename: Nienke
authors.initials: N
authors.lastname: Wolterbeek
authors.forename: Anouk J M
authors.initials: AJ
authors.lastname: Fermont
authors.forename: Henk
authors.initials: H
authors.lastname: van Mameren
authors.forename: Heleen
authors.initials: H
authors.lastname: Sonneveld
authors.forename: Sharon
authors.initials: S
authors.lastname: Griffin
authors.forename: Rob A
authors.initials: RA
authors.lastname: de Bie
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001134:Arm Injuries / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D011446:Prospective Studies; D017006:Rotator Cuff; D012720:Severity of Illness Index