Development and Psychometric Characteristics of the TBI-QOL Independence Item Bank and Short Form and the TBI-QOL Asking for Help Scale

Abstract

ObjectiveTo develop an item response theory (IRT)-calibrated, patient-reported outcome measure of subjective independence for individuals with traumatic brain injury (TBI). DesignLarge-scale item calibration field testing; confirmatory factor analysis (CFA) and graded response model IRT analyses. SettingFive TBI Model System centers across the United States. ParticipantsAdults with complicated mild, moderate, or severe TBI (N=556). Outcome MeasuresTraumatic Brain Injury–Quality of Life (TBI-QOL) Independence item bank and the TBI-QOL Asking for Help scale. ResultsA total of 556 individuals completed 44 items in the Independence item pool. Initial factor analyses indicated that items related to the idea of “asking for help” were measuring a different construct from other items in the pool. These 9 items were set aside. Twenty-two other items were removed because of bimodal distributions and/or low item-total correlations. CFA supported unidimensionality of the remaining Independence items. Graded response model IRT analysis was used to estimate slopes and thresholds for the final 13 Independence items. An 8-item fixed-length short form was also developed. The 9 Asking for Help items were analyzed separately. One misfitting item was deleted, and the final 8 items became a fixed-length IRT-calibrated scale. Reliability was high for both measures. ConclusionsThe IRT-calibrated TBI-QOL Independence item bank and short form and TBI-QOL Asking for Help scale may be used to measure important issues for individuals with TBI in research and clinical applications.