Primary objectives: The high-level mobility assessment tool (HiMAT) was developed to measure high-level mobility limitations following traumatic brain injury (TBI). Rasch analysis was used in the development to ensure cognitive deficits would have a minimal impact on performance. The main aim of this study was to investigate the dimensionality of the HiMAT using recently developed advanced testing procedures.
Research design: Results from the original sample of 103 adults with TBI used to develop the HiMAT were re-analysed using the RUMM2020 program. Revised minimal detectable change (MDC(95)) scores were also calculated.
Main outcomes and results: Rasch analysis of all 13 HiMAT items suggested that the scale was multidimensional, showing a clear separation between the stair and non-stair items. The nine non-stair items of the HiMAT showed good overall fit, excellent internal consistency, with no disordered thresholds or misfitting items, however removal of one item was required to ensure a unidimensional scale. The final 8-item solution showed good model fit (p = 0.93), excellent internal consistency (PSI = 0.96), no disordered thresholds, no misfitting items and no differential item functioning for age or sex. The revised HiMAT total score is 32 points and the MDC(95) was calculated to be +/-2 points.
Conclusion: The results of this study demonstrate that the revised HiMAT is unidimensional and valid to use in rehabilitation and community settings where there is no access to stairs.