Brain Injury Functional Outcome Measure (BI-FOM): A Single Instrument Capturing the Range of Recovery in Moderate-Severe Traumatic Brain Injury

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.