The Functional Gait Assessment in Older Adults: Validation Through Rasch Modeling

Background The Functional Gait Assessment (FGA), a measure of walking balance ability, was developed to eliminate the ceiling effect observed in the Dynamic Gait Index (DGI). Three presumably more difficult tasks were added and 1 easier task was removed from the original 8 DGI tasks. The effects of these modifications on item hierarchy have not previously been analyzed. Objective The purpose of this study was to determine: (1) the ordering of the 10 FGA tasks and the extent to which they map along a clinically logical difficulty continuum, (2) whether the spread of tasks is sufficient to measure patients of varying functional ability levels without a ceiling effect, (3) where the 3 added tasks locate along the task difficulty continuum, and (4) the psychometric properties of the individual FGA tasks. Design A retrospective chart review was conducted. Methods Functional Gait Assessment scores from 179 older adults referred for physical therapy for balance retraining were analyzed by Rasch modeling. Results The FGA task hierarchy met clinical expectations, with the exception of the “walking on level” task, which locates in the middle of the difficulty continuum. There was no ceiling effect. Two of the 3 added tasks were the most difficult FGA tasks. Performance on the most difficult task (“gait with narrow base of support”) demonstrated greater variability than predicted by the Rasch model. Limitations The sample was limited to older adults who were community dwelling and independently ambulating. Findings cannot be generalized to other patient groups. Conclusions The revised scoring criteria of the FGA may have affected item hierarchy. The results suggest that the FGA is a measure of walking balance ability in older adults that is clinically appropriate and has construct validity. Administration of the FGA may be modified further to improve administration efficiency.