Examination of the Applicability of the Disabilities of the Arm, Shoulder and Hand (DASH) Questionnaire to Patients with Hand Injuries and Diseases Using Rasch Analysis.

BACKGROUND: The Disabilities of the Arm, Shoulder and Hand (DASH) Questionnaire is the most commonly applied patient-reported outcome measure used to assess disability and functioning in clinical research and practice for patients with injuries and diseases of the upper extremities. The objective of this study was to assess whether the DASH is a valid and reliable questionnaire to measure disability and functioning in patients with hand injuries and diseases using Rasch analysis.

METHODS: We performed a psychometric study using data derived from two multicentre studies carried out to develop the International Classification of Functioning, Disability and Health (ICF) Core Sets for Hand Conditions. We analysed the data of 417 patients recruited in a clinical setting and suffering from hand injuries (e.g. finger fracture, flexor tendon injury) or diseases (e.g. carpal tunnel syndrome, rhizarthrosis). We examined whether the DASH fulfilled the assumptions for its use as a measure by applying a partial credit model and testing for differential item functioning for sex and age.

RESULTS: Bifactor analysis revealed problems with the underlying latent trait of functioning and disability. Rasch analysis raised further issues, including disordered thresholds for eight items and misfit in nine items. One item showed Differential Item Functioning for sex.

CONCLUSION: The study reveals that some DASH items do not fit the underlying trait that the DASH aims to measure. Further studies using Rasch analysis are needed to compare our findings with results of studies involving other target groups (e.g. patients with injuries of the upper arm and shoulder).