Rasch analysis of the brief Michigan Hand Questionnaire in patients with thumb osteoarthritis

The brief Michigan Hand Questionnaire (brief MHQ) is a 12-item self-reported measure of hand function for patients with hand disorders which has been validated using Classical Test Theory. Rasch analysis can provide more detailed psychometric information. The purpose of this Rasch analysis is to assess the psychometric properties of the brief MHQ for patients with thumb osteoarthritis, and to make recommendations for improvements to the questionnaire if needed. METHODS: The Michigan Hand Questionnaire and demographic data were collected from 923 thumb osteoarthritis patients treated in specialized clinics for hand surgery and therapy in the Netherlands. Rasch analysis was performed on the 12 items of the brief MHQ using RUMM 2030 to assess the fit of the brief MHQ to the Rasch model. To determine fit, analysis of fit summary statistics, individual person fit and individual item fit were assessed. Threshold distributions were assessed to identify if any items required rescoring. The Person Separation Index was calculated to measure reliability of the questionnaire. Differential item functioning was assessed to identify item bias, and Principal Component Analysis was performed to identify unidimensionality and local dependence. The brief MHQ showed misfit (χ = 1312.5, p