title: Toward standardized reporting for a cohort study on functioning: The Swiss Spinal Cord Injury Cohort Study.
abstract: OBJECTIVE
  Functioning is an important outcome to measure in cohort studies. Clear and operational outcomes are needed to judge the quality of a cohort study. This paper outlines guiding principles for reporting functioning in cohort studies and addresses some outstanding issues.
  
  
  METHODS
  Principles of how to standardize reporting of data from a cohort study on functioning, by deriving scores that are most useful for further statistical analysis and reporting, are outlined. The Swiss Spinal Cord Injury Cohort Study Community Survey serves as a case in point to provide a practical application of these principles.
  
  
  RESULTS
  Development of reporting scores must be conceptually coherent and metrically sound. The International Classification of Functioning, Disability and Health (ICF) can serve as the frame of reference for this, with its categories serving as reference units for reporting. To derive a score for further statistical analysis and reporting, items measuring a single latent trait must be invariant across groups. The Rasch measurement model is well suited to test these assumptions.
  
  
  CONCLUSIONS
  Our approach is a valuable guide for researchers and clinicians, as it fosters comparability of data, strengthens the comprehensiveness of scope, and provides invariant, interval-scaled data for further statistical analyses of functioning.
authors.affiliation: ICF Unit, Swiss Paraplegic Research, CH-6207 Nottwil, Switzerland. E-mail: birgit.prodinger@paraplegie.ch.
authors.forename: Birgit
authors.initials: B
authors.lastname: Prodinger
authors.forename: Carolina S
authors.initials: CS
authors.lastname: Ballert
authors.forename: Mirjam
authors.initials: M
authors.lastname: Brach
authors.forename: Martin W G
authors.initials: MW
authors.lastname: Brinkhof
authors.forename: Alarcos
authors.initials: A
authors.lastname: Cieza
authors.forename: Kerstin
authors.initials: K
authors.lastname: Hug
authors.forename: Xavier
authors.initials: X
authors.lastname: Jordan
authors.forename: Marcel W M
authors.initials: MW
authors.lastname: Post
authors.forename: Anke
authors.initials: A
authors.lastname: Scheel-Sailer
authors.forename: Martin
authors.initials: M
authors.lastname: Schubert
authors.forename: Alan
authors.initials: A
authors.lastname: Tennant
authors.forename: Gerold
authors.initials: G
authors.lastname: Stucki
mesh_terms: D000328:Adult; D015331:Cohort Studies; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D064702:International Classification of Functioning, Disability and Health; D008297:Male; D008875:Middle Aged; D000071066:Patient Reported Outcome Measures; D012107:Research Design; D013119:Spinal Cord Injuries / Q000145:classification*; D011795:Surveys and Questionnaires / Q000592:standards*; D013557:Switzerland