Reliability and Construct Validity of the Japanese Version of the Posture and Postural Ability Scale in Individuals with Cerebral Palsy.

Objective: This study aimed to develop the Japanese version of the Posture and Postural Ability Scale (PPAS) and verify its inter- and intra-rater reliability, construct validity, and internal consistency in individuals with cerebral palsy (CP) in Japan.

Methods: This cross-sectional study recruited 73 children and adults with CP at all Gross Motor Function Classification System (GMFCS) levels. The translation procedure was performed by three Japanese physiotherapists and the developer of the original version. Intra- and inter-rater reliability were evaluated using the weighted kappa coefficients, and construct validity was based on the correlation coefficients between PPAS and GMFCS. Cronbach's alpha coefficients were calculated to assess internal consistency.

Results: Weighted kappa coefficients for intra- and inter-rater reliability exceeded 0.81 for all items. The correlation coefficients between the PPAS and GMFCS were negative and showed "moderate" to "very strong" in almost all items (ρ = -0.66 to -0.91), except for one item (ρ = -0.37). Cronbach's alpha coefficients exceeded 0.80 in all four positions.

Conclusion: This study supports the Japanese version of the PPAS with excellent intra- and inter-rater reliability, good construct validity, and internal consistency in the Japanese CP population.