title: Linking the activity measure for post acute care and the quality of life outcomes in neurological disorders.
abstract: OBJECTIVE
  To use item response theory (IRT) methods to link physical functioning items in the Activity Measure for Post Acute Care (AM-PAC) and the Quality of Life Outcomes in Neurological Disorders (Neuro-QOL).
  
  
  METHODS
  Secondary data analysis of the physical functioning items of AM-PAC and Neuro-QOL. We used a nonequivalent group design with 36 core items common to both instruments and a test characteristic curve transformation method for linking AM-PAC and Neuro-QOL scores. Linking was conducted so that both raw and scaled AM-PAC and Neuro-QOL scores (mean ± SD converted-logit scores, 50 ± 10) could be compared.
  
  
  METHODS
  AM-PAC items were administered to rehabilitation patients in post-acute care (PAC) settings. Neuro-QOL items were administered to a community sample of adults through the Internet.
  
  
  METHODS
  PAC patients (N=1041) for the AM-PAC sample and community-dwelling adults (N=549) for the Neuro-QOL sample.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Mobility (N=25) and activity of daily living (ADL) items (N=11) common to both instruments were included in analysis.
  
  
  RESULTS
  Neuro-QOL items were linked to the AM-PAC scale by using the generalized partial credit model. Mobility and ADL subscale scores from the 2 instruments were calibrated to the AM-PAC metric.
  
  
  CONCLUSIONS
  An IRT-based linking method placed AM-PAC and Neuro-QOL mobility and ADL scores on a common metric. This linking allowed estimation of AM-PAC mobility and ADL subscale scores based on Neuro-QOL mobility and ADL subscale scores and vice versa. The accuracy of these results should be validated in a future sample in which participants respond to both instruments.
authors.affiliation: Health and Disability Research Institute, Boston University School of Public Health, Boston, MA 02118, USA.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Haley
authors.forename: Pengsheng
authors.initials: P
authors.lastname: Ni
authors.forename: Jin-Shei
authors.initials: JS
authors.lastname: Lai
authors.forename: Feng
authors.initials: F
authors.lastname: Tian
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Coster
authors.forename: Alan M
authors.initials: AM
authors.lastname: Jette
authors.forename: Donald
authors.initials: D
authors.lastname: Straub
authors.forename: David
authors.initials: D
authors.lastname: Cella
mesh_terms: D000203:Activities of Daily Living; D000208:Acute Disease; D002138:Calibration; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007256:Information Systems; D020407:Internet; D008297:Male; D009316:National Institutes of Health (U.S.); D009422:Nervous System Diseases / Q000534:rehabilitation*; D017063:Outcome Assessment, Health Care; D011788:Quality of Life; D020127:Recovery of Function; D012046:Rehabilitation / Q000592:standards*; D012650:Self Disclosure; D011795:Surveys and Questionnaires; D014481:United States