title: Development of a self-report physical function instrument for disability assessment: item pool construction and factor analysis.
abstract: OBJECTIVE
  To build a comprehensive item pool representing work-relevant physical functioning and to test the factor structure of the item pool. These developmental steps represent initial outcomes of a broader project to develop instruments for the assessment of function within the context of Social Security Administration (SSA) disability programs.
  
  
  METHODS
  Comprehensive literature review; gap analysis; item generation with expert panel input; stakeholder interviews; cognitive interviews; cross-sectional survey administration; and exploratory and confirmatory factor analyses to assess item pool structure.
  
  
  METHODS
  In-person and semistructured interviews and Internet and telephone surveys.
  
  
  METHODS
  Sample of SSA claimants (n=1017) and a normative sample of adults from the U.S. general population (n=999).
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Model fit statistics.
  
  
  RESULTS
  The final item pool consisted of 139 items. Within the claimant sample, 58.7% were white; 31.8% were black; 46.6% were women; and the mean age was 49.7 years. Initial factor analyses revealed a 4-factor solution, which included more items and allowed separate characterization of: (1) changing and maintaining body position, (2) whole body mobility, (3) upper body function, and (4) upper extremity fine motor. The final 4-factor model included 91 items. Confirmatory factor analyses for the 4-factor models for the claimant and the normative samples demonstrated very good fit. Fit statistics for claimant and normative samples, respectively, were: Comparative Fit Index=.93 and .98; Tucker-Lewis Index=.92 and .98; and root mean square error approximation=.05 and .04.
  
  
  CONCLUSIONS
  The factor structure of the physical function item pool closely resembled the hypothesized content model. The 4 scales relevant to work activities offer promise for providing reliable information about claimant physical functioning relevant to work disability.
authors.affiliation: Health and Disability Research Institute, Department of Health Policy and Management, School of Public Health, Boston University Medical Campus, Boston, MA, USA. cmm@bu.edu
authors.forename: Christine M
authors.initials: CM
authors.lastname: McDonough
authors.forename: Alan M
authors.initials: AM
authors.lastname: Jette
authors.forename: Pengsheng
authors.initials: P
authors.lastname: Ni
authors.forename: Kara
authors.initials: K
authors.lastname: Bogusz
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Marfeo
authors.forename: Diane E
authors.initials: DE
authors.lastname: Brandt
authors.forename: Leighton
authors.initials: L
authors.lastname: Chan
authors.forename: Mark
authors.initials: M
authors.lastname: Meterko
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Haley
authors.forename: Elizabeth K
authors.initials: EK
authors.lastname: Rasch
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D006233:Persons with Disabilities; D005121:Extremities; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D026741:Physical Therapy Modalities; D011594:Psychometrics; D015203:Reproducibility of Results; D057566:Self Report; D012959:Socioeconomic Factors; D014481:United States; D019131:United States Social Security Administration
keywords: CAT; CFA; CFI; Disability evaluation; Disabled persons; EFA; Factor analysis, statistical; ICF; IRT; Insurance; International Classification of Functioning, Disability and Health; PROMIS; Patient-Reported Outcomes Measurement Information System; Questionnaires; RMSEA; Rehabilitation; SCI-FI; SSA; Social Security Administration; Spinal Cord Injury-Functional Index; TLI; Tucker-Lewis Index; comparative fit index; computer-adaptive testing; confirmatory factor analysis; exploratory factor analysis; item response theory; root mean square error of approximation
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