Development and Initial Evaluation of a Fine Motor Subscale of a Comprehensive Developmental Scale for Children Aged 18–41 Months

Identifying developmental delays in children is vital for timely intervention, yet there are limited local developmental tests in Hong Kong that include a fine motor subscale and are specifically tailored for children aged 18–41 months. To address this need, we developed a 50-item fine motor subscale, which underwent two rounds of pilot testing and expert reviews. This study investigated its internal-scale validity and reliability, comprising 340 young children in Hong Kong, including 82 children with fine motor delays and 258 typical developing children. Unidimensionality and test targeting, known-group validity, and internal consistency of this subscale were examined. The Rasch analysis supported the unidimensionality of the fine motor subscale which accounted for 63.9% of the total variance. Most items, except two, showed a good fit, and the item difficulty levels (between −5.91 and 5.63 logits) effectively covered children’s ability levels (between −7.17 and 5.04 logits). Subscale scores significantly differed across age groups and between children with and without fine motor delays. The internal consistency was high at 0.96. This study provides initial psychometric evidence for the newly developed fine motor subscale, with ongoing refinement and validation aimed at establishing the final version of the Hong Kong Comprehensive Assessment Scales for Toddlers.