Objective: To develop a measure of global functioning after moderate-severe TBI with similar measurement precision but a longer measurement range than the FIM.
Design: Phase 1: retrospective analysis of 5 data sets containing FIM, Disability Rating Scale, and other assessment items to identify candidate items for extending the measurement range of the FIM; Phase 2: prospective administration of 49 candidate items from phase 1, with Rasch analysis to identify a unidimensional scale with an extended range.
Setting: Six TBI Model System rehabilitation hospitals.
Participants: Individuals (N=184) with moderate-severe injury recruited during inpatient rehabilitation or at 1-year telephone follow-up.
Interventions: Participants were administered the 49 assessment items in person or via telephone.
Main outcome measures: Item response theory parameters: item monotonicity, infit/outfit statistics, and Factor 1 variance.
Results: After collapsing misordered rating categories and removing misfitting items, we derived the Brain Injury Functional Outcome Measure (BI-FOM), a 31-item assessment instrument with high reliability, greatly extended measurement range, and improved unidimensionality compared with the FIM.
Conclusions: The BI-FOM improves global measurement of function after moderate-severe brain injury. Its high precision, relative lack of floor and ceiling effects, and feasibility for telephone follow-up, if replicated in an independent sample, are substantial advantages.
Keywords: Assessment; Brain injuries; Outcome Measurement; Patient outcome; Rehabilitation.
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