Face and construct validity of the Gait Deviation Index in adults with spastic cerebral palsy

Abstract

Objective: To investigate face and construct validity of the Gait Deviation Index (GDI) in adults with spastic cerebral palsy. The International Classification of Functioning, Disability and Health (ICF) was used as a framework, defining gait and walking as the manner or style of walking (?body function?), and the execution of gait (?activity?), respectively. Design: A cross-sectional study. Methods: Participants: 66 adults with spastic cerebral palsy, mean age 37 years, and previously collected data on 50 healthy adults (reference population). Variables: GDI from three-dimensional gait analysis, Gross Motor Function Classification System (GMFCS), 6-min walk test (6MWT), Timed Up and Go (TUG), and Physiological Cost Index (PCI). Results: Mean GDI was 74. 3 in adults with cerebral palsy, and 101. 1 in the reference population. A significant difference in GDI was found between the reference population and GMFCS level I (p < 0. 001), between I and II (p < 0. 001), but not between II and III (p = 0. 633). The associations between GDI and 6MWT, TUG and PCI were r = 0. 30, r = ?0. 30, and r = ?0. 56, respectively. Conclusion: GDI demonstrated similar distributional properties as those reported in children with cerebral palsy, suggesting satisfactory face validity. Low correlations between GDI and 6MWT/TUG reflect that gait and functional walking/mobility are different constructs, implicating the importance of selecting outcomes in all ICF domains when evaluating walking ability in adults with spastic cerebral palsy.