title: Classical test theory and Rasch analysis validation of the Upper Limb Functional Index in subjects with upper limb musculoskeletal disorders.
abstract: OBJECTIVE
  To perform a comprehensive analysis of the psychometric properties and dimensionality of the Upper Limb Functional Index (ULFI) using both classical test theory and Rasch analysis (RA).
  
  
  METHODS
  Prospective, single-group observational design.
  
  
  METHODS
  Freestanding rehabilitation center.
  
  
  METHODS
  Convenience sample of Italian-speaking subjects with upper limb musculoskeletal disorders (N=174).
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  The Italian version of the ULFI. Data were analyzed using parallel analysis, exploratory factor analysis, and RA for evaluating dimensionality, functioning of rating scale categories, item fit, hierarchy of item difficulties, and reliability indices.
  
  
  RESULTS
  Parallel analysis revealed 2 factors explaining 32.5% and 10.7% of the response variance. RA confirmed the failure of the unidimensionality assumption, and 6 items out of the 25 misfitted the Rasch model. When the analysis was rerun excluding the misfitting items, the scale showed acceptable fit values, loading meaningfully to a single factor. Item separation reliability and person separation reliability were .98 and .89, respectively. Cronbach alpha was .92.
  
  
  CONCLUSIONS
  RA revealed weakness of the scale concerning dimensionality and internal construct validity. However, a set of 19 ULFI items defined through the statistical process demonstrated a unidimensional structure, good psychometric properties, and clinical meaningfulness. These findings represent a useful starting point for further analyses of the tool (based on modern psychometric approaches and confirmatory factor analysis) in larger samples, including different patient populations and nationalities.
authors.affiliation: School in Advanced Sciences and Technology in Rehabilitation Medicine and Sports, Tor Vergata University, Rome, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Bravini
authors.affiliation: Unit of Occupational Rehabilitation and Ergonomics, Salvatore Maugeri Foundation, Scientific Institute of Veruno, Veruno, Italy.
authors.forename: Franco
authors.initials: F
authors.lastname: Franchignoni
authors.affiliation: Unit of Bioengineering, Salvatore Maugeri Foundation, Scientific Institute of Veruno, Veruno, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Giordano
authors.affiliation: Unit of Occupational Rehabilitation and Ergonomics, Salvatore Maugeri Foundation, Scientific Institute of Veruno, Veruno, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Sartorio
authors.affiliation: Unit of Occupational Rehabilitation and Ergonomics, Salvatore Maugeri Foundation, Scientific Institute of Veruno, Veruno, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Ferriero
authors.affiliation: Unit of Occupational Rehabilitation and Ergonomics, Salvatore Maugeri Foundation, Scientific Institute of Veruno, Veruno, Italy. Electronic address: stefano.vercelli@fsm.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Vercelli
authors.affiliation: Department of Physical and Rehabilitation Medicine, Tor Vergata University Hospital, Rome, Italy.
authors.forename: Calogero
authors.initials: C
authors.lastname: Foti
mesh_terms: D000328:Adult; D000368:Aged; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D009140:Musculoskeletal Diseases / Q000503:physiopathology* / Q000523:psychology*; D011446:Prospective Studies; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D034941:Upper Extremity / Q000503:physiopathology*
keywords: Disability evaluation; Musculoskeletal diseases; Outcome assessment (health care); Psychometrics; Rehabilitation