Rasch analysis of the assessment of children's hand skills in children with and without disabilities.

The Assessment of Children's Hand Skills (ACHS) is a new assessment tool that utilizes a naturalistic observational method to capture children's real-life hand skill performance when engaging in various types of activities. The ACHS also intends to be used with both typically developing children and those presenting with disabilities. The purpose of this study was to further investigate the construct validity of the ACHS using the Rasch analysis. Participants included 64 typically developing children and 70 children with disabilities in the age range of 2-12 years. Rasch analysis results confirmed the appropriateness of the ACHS's 6-level rating scale in this combined group of children. All 22 activity items and 19 of the 20 hand skill items in the ACHS formed a unidimensional scale and were ordered according to difficulty as clinically and developmentally expected. The ACHS also exhibited sufficient response validity and item-difficulty range when applied to children with disabilities as well as typically developing, preschool-age children. Furthermore, less than half of the ACHS items were found to exhibit differential item functioning with regard to gender (5 activity items) and disability (2 activity items and 7 hand skill items). Therefore, the ACHS shows preliminary evidence of construct validity for its clinical use in assessing children's hand skill performance in real-life contexts.