title: Development of a computer-adaptive physical function instrument for Social Security Administration disability determination.
abstract: OBJECTIVE
  To develop and test an instrument to assess physical function for Social Security Administration (SSA) disability programs, the SSA-Physical Function (SSA-PF) instrument. Item response theory (IRT) analyses were used to (1) create a calibrated item bank for each of the factors identified in prior factor analyses, (2) assess the fit of the items within each scale, (3) develop separate computer-adaptive testing (CAT) instruments for each scale, and (4) conduct initial psychometric testing.
  
  
  METHODS
  Cross-sectional data collection; IRT analyses; CAT simulation.
  
  
  METHODS
  Telephone and Internet survey.
  
  
  METHODS
  Two samples: SSA claimants (n=1017) and adults from the U.S. general population (n=999).
  
  
  METHODS
  None.
  
  
  METHODS
  Model fit statistics, correlation, and reliability coefficients.
  
  
  RESULTS
  IRT analyses resulted in 5 unidimensional SSA-PF scales: Changing & Maintaining Body Position, Whole Body Mobility, Upper Body Function, Upper Extremity Fine Motor, and Wheelchair Mobility for a total of 102 items. High CAT accuracy was demonstrated by strong correlations between simulated CAT scores and those from the full item banks. On comparing the simulated CATs with the full item banks, very little loss of reliability or precision was noted, except at the lower and upper ranges of each scale. No difference in response patterns by age or sex was noted. The distributions of claimant scores were shifted to the lower end of each scale compared with those of a sample of U.S. adults.
  
  
  CONCLUSIONS
  The SSA-PF instrument contributes important new methodology for measuring the physical function of adults applying to the SSA disability programs. Initial evaluation revealed that the SSA-PF instrument achieved considerable breadth of coverage in each content domain and demonstrated noteworthy psychometric properties.
authors.affiliation: Department of Health Policy and Management, The Health and Disability Research Institute, School of Public Health, Boston University Medical Campus, Boston, MA, USA. psni@bu.edu
authors.forename: Pengsheng
authors.initials: P
authors.lastname: Ni
authors.forename: Christine M
authors.initials: CM
authors.lastname: McDonough
authors.forename: Alan M
authors.initials: AM
authors.lastname: Jette
authors.forename: Kara
authors.initials: K
authors.lastname: Bogusz
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Marfeo
authors.forename: Elizabeth K
authors.initials: EK
authors.lastname: Rasch
authors.forename: Diane E
authors.initials: DE
authors.lastname: Brandt
authors.forename: Mark
authors.initials: M
authors.lastname: Meterko
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Haley
authors.forename: Leighton
authors.initials: L
authors.lastname: Chan
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D006233:Persons with Disabilities; D005121:Extremities; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008603:Mental Health; D008875:Middle Aged; D051346:Mobility Limitation; D026741:Physical Therapy Modalities; D011594:Psychometrics; D015203:Reproducibility of Results; D012737:Sex Factors; D012943:Social Security; D014481:United States
keywords: CAT; DIF; Disability evaluation; Disabled persons; Health Status Indicators; IRT; Insurance; PROMIS; Patient-Reported Outcomes Measurement Information System; Psychometrics; Questionnaires; Rehabilitation; SSA; SSA-PF; Social Security Administration; Social Security Administration Physical Function; Statistical model; computer-adaptive testing; differential item functioning; item response theory