Multidimensional Rasch validation of the Frenchay Activities Index in stroke patients receiving rehabilitation.

OBJECTIVE To validate the dimensionality, hierarchical properties, and reliability of the Frenchay Activities Index. DESIGN Self-report survey of patients with stroke. PATIENTS A total of 127 patients provided 254 observations before and after treatments. METHODS Multidimensional Rasch model was conducted. RESULTS The 2-factor model showed the significantly smallest deviance and fitted the data best among 6 possible models. The 2-factor structure was stable before and after treatments, after the rating scale was revised from 4 points to 3 points. Differential item functioning relevant to the time since stroke was detected for 2 tasks. The item difficulty hierarchy of the 2 domains was determined. The correlation between the 2 domains was 0.58. The scale demonstrated acceptable ceiling and floor effects. The overall person (separation) reliability was 0.99. The reliabilities for the 2 domains were 0.81 and 0.73. CONCLUSION The Frenchay Activities Index is a useful 2-dimensional scale for evaluating daily functions in stroke patients. The item difficulty hierarchy and significant differential item functioning related to the time since stroke might reflect the changes in the recovery course after stroke. The Frenchay Activities Index could be improved by adding items to capture patients with high and low levels of daily activities in domestic chores.