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

OBJECTIVE

To develop an item response theory (IRT)-calibrated, patient-reported outcome measure of subjective independence for individuals with traumatic brain injury (TBI).

DESIGN

Large-scale item calibration field testing; confirmatory factor analysis (CFA) and graded response model IRT analyses.

SETTING

Five TBI Model System centers across the United States.

PARTICIPANTS

Adults with complicated mild, moderate, or severe TBI (N=556).

OUTCOME MEASURES

Traumatic Brain Injury-Quality of Life (TBI-QOL) Independence item bank and the TBI-QOL Asking for Help scale.

RESULTS

A 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.

CONCLUSIONS

The 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.