Rasch analysis of the World Health Organization Disability Assessment Schedule 2.0 in a mild traumatic brain injury sample

In this study we examined the psychometric properties of the World Health Organization Disability Assessment Schedule (WHODAS 2.0 12-item version) in a mild traumatic brain injury (MTBI) sample. Materials and Methods: Treatment-seeking adults (n = 131) with MTBI recruited from outpatient clinics in Vancouver Canada, were assessed 1- and 3-months following clinic intake. Dimensionality, reliability, and differential item functioning of the WHODAS 2.0 were examined with Rasch analysis. Associations between change in WHODAS 2.0 scores and symptom, work and perceived improvement outcomes were examined. Results: Adequate fit to the Rasch model was achieved for 1-month follow-up assessment WHODAS 2.0 scores without altering the response format or item content [X-2 (24, n = 130) = 21.2, p = .6]. The best model fit for 3-month follow-up assessment scores was achieved when two items (problems with dressing and washing) were combined [X-2 (22, n = 115) = 20.9, p = .5]. Associations were evident between changes in WHODAS total Rasch scores and other outcome indicators such as return to productivity and percieved improvement. Conclusions: The WHODAS 2.0 (12-item version) is a psychometrically sound measure of functional outcome for adults seeking treatment following MTBI. Our table of ordinal to interval score conversions is recommended for future research examining MTBI outcomes.