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

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 while one easier task was removed from the original eight DGI tasks. The effects of these modifications on item hierarchy have not previously been analyzed. The objective of this study was to determine: (1) the ordering of the ten FGA tasks and the extent to which they map along a clinically logical difficulty continuum, (2) if the spread of tasks is sufficient to measure patients of varying functional ability levels without a ceiling effect, (3) where the three added tasks locate along the task difficulty continuum, and (4) the psychometric properties of the individual FGA tasks. FGA scores from 179 older adults referred to physical therapy for balance retraining analyzed by Rasch modeling. 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 three 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.

In conclusion the revised scoring criteria of the FGA may have affected item hierarchy. Results suggest that the FGA is a clinically appropriate and construct valid measure of walking balance ability in older adults. Administration of the FGA may be modified further to improve administration efficiency.