title: A Multidimensional Rasch Analysis of the Functional Independence Measure Based on the National Institute on Disability, Independent Living, and Rehabilitation Research Traumatic Brain Injury Model Systems National Database.
abstract: A number of studies have evaluated the psychometric properties of the Functional Independence Measure (FIM™) using Rasch analysis, although none has done so using the National Institute on Disability, Independent Living, and Rehabilitation Research Traumatic Brain Injury Model Systems National Database, a longitudinal database that captures demographic and outcome information on persons with moderate to severe traumatic brain injury across the United States. In the current study, we examine the psychometric properties of the FIM as represented by persons within this database and demonstrate that the FIM comprises three subscales representing cognitive, self-care, and mobility domains. These subscales were analyzed simultaneously using a multivariate Rasch model in combination with a time dependent concurrent calibration scheme with the goal of creating a raw score-to-logit transformation that can be used to improve the accuracy of parametric statistical analyses. The bowel and bladder function items were removed because of misfit with the motor and cognitive items. Some motor items exhibited step disorder, which was addressed by collapsing Categories 1-3 for Toileting, Stairs, Locomotion, Tub/Shower Transfers; Categories 1 and 2 for Toilet and Bed Transfers; and Categories 2 and 3 for Grooming. The strong correlations (r = 0.82-0.96) among the three subscales suggest they should be modeled together. Coefficient alpha of 0.98 indicates high internal consistency. Keyform maps are provided to enhance clinical interpretation and application of study results.
authors.affiliation: 1 Craig Hospital , Englewood, Colorado.|2 Traumatic Brain Injury National Statistical and Data Center , Englewood, Colorado.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Pretz
authors.affiliation: 3 Center for Health Information and Communication, Richard L. Roudebush VA Medical Center , Indianapolis, Indiana.|4 Department of Physical Medicine and Rehabilitation, Indiana University School of Medicine , Indianapolis, Indiana.
authors.forename: Jacob
authors.initials: J
authors.lastname: Kean
authors.affiliation: 5 Center for Rehabilitation Outcomes Research, Rehabilitation Institute of Chicago , Chicago Illinois.|6 Department of Physical Medicine and Rehabilitation, Feinberg Medical School, Northwestern University , Chicago, Illinois.
authors.forename: Allen W
authors.initials: AW
authors.lastname: Heinemann
authors.affiliation: 7 Icahn School of Medicine at Mount Sinai , New York, New York.
authors.forename: Allan J
authors.initials: AJ
authors.lastname: Kozlowski
authors.affiliation: 5 Center for Rehabilitation Outcomes Research, Rehabilitation Institute of Chicago , Chicago Illinois.
authors.forename: Rita K
authors.initials: RK
authors.lastname: Bode
authors.affiliation: 8 Australian Council for Educational Research , Camberwell, Victoria, Australia .
authors.forename: Eveline
authors.initials: E
authors.lastname: Gebhardt
mesh_terms: D000328:Adult; D000070642:Brain Injuries, Traumatic / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology / Q000534:rehabilitation; D003627:Data Interpretation, Statistical; D016208:Databases, Factual / Q000706:statistics & numerical data; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011594:Psychometrics / Q000295:instrumentation*; D015599:Trauma Severity Indices; D014481:United States; D055815:Young Adult
keywords: Rasch analysis; measurement; rehabilitation outcome; traumatic brain injury