Objective: To evaluate the validity and item unidimensionality of the Rivermead Mobility Index (RMI) by using Rasch analysis.
Design: Application of Rasch analysis on the RMI partial data set.
Setting: A stroke program at a rehabilitation hospital in Italy.
Participants: A total of 308 consecutive patients (155 women, 153 men; avg age, 62.79+/-11.94 y) hospitalized between 1990 and 1996. Average interval between stroke onset and admission was 52.48+/-36.22 days.
Intervention: Medical inpatient rehabilitation.
Main outcome measures: Patients' mobility status was assessed using the RMI administered at admission and discharge. Ratings were assigned by 4 staff members working as a team. We performed separate Rasch analyses on the RMI data, gathered from different groups of first stroke inpatients examined before and after rehabilitation treatment.
Results: asch analysis showed the overall good validity of the RMI, except for item 15, which did not fit the unidimensional continuum estimated through the Rasch rating model.
Conclusion: The RMI is a unidimensional scale with a hierarchy of easy-to-hard test questions. Item difficulty level was stable when processed on different groups of patients assessed on different occasions.
Copyright 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation