Psychometric measurement properties of the world health organization disability assessment schedule 2.0 (WHODAS) evaluated among veterans with mild traumatic brain injury and behavioral health conditions

Purpose: Examine the psychometric properties of the World Health Organization Disability Assessment Schedule 2.0 among U.S. Iraq/Afghanistan Veterans with a combination of mild traumatic brain injury and behavioral health conditions using Rasch analysis. Methods: 307 Veterans were classified as either combat control (n = 141), or one of three clinical groups: mild traumatic brain injury (n = 10), behavioral health conditions (n = 24), or both (n = 128). Data from the three clinical groups were used to establish step and item calibrations serving as anchors when including the control group. Results: Measurement precision was excellent (person separation reliability = 0.93). Ordering of item calibrations formed a logical hierarchy. Test items were off-target (too easy) for the clinical groups. Principal component analysis indicated unidimensionality although 4/36 items misfit the measurement model. No meaningful differential item functioning was detected. There was a moderate effect size (Hedge’s g = 1.64) between the control and clinical groups. Conclusions: The World Health Organization Disability Assessment Schedule was suitable for our study sample, distinguishing 4 levels of functional ability. Although items may be easy for some Veterans with mild traumatic brain injury and/or behavioral health conditions, the World Health Organization Disability Assessment Schedule can be used to capture disability information for those with moderate to severe disability.Implications for rehabilitation Persistent functional disability is seen in military and civilian populations with mild traumatic brain injury which often co-occurs with behavioral health conditions. A comprehensive measure of disability is needed to distinguish between levels of disability to inform clinical decisions for individual patients and to detect treatment effects between groups in research. Results of this analysis indicate the World Health Organization Disability Assessment Schedule items are sufficiently unidimensional to evaluate level of disability in the moderate and severe range among persons with mild traumatic brain injury with and without behavioral health conditions. Further examination of the psychometric properties of the World Health Organization. Disability Assessment Schedule is necessary before measurement of disability is recommended for those with less than moderate levels of disability.