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Rasch analysis of the Rivermead Mobility Index: a study using mobility measures of first-stroke inpatients
Gabriella Antonucci1, Teresa Aprile, Stefano Paolucci
1IRCCS-Fondazione Santa Lucia and Department of Psychology, University of Rome La Sapienza, Rome, Italy. gabriella.antonucci@uniroma1.it
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.