Validating a universal measurement scale and standardized, reproducible unit for gross motor development.

Objective: To validate a universal measurement scale and unit for gross motor development across multiple instruments.

Design: Retrospective cohorts SETTING: Community and clinic PARTICIPANTS: Item difficulty calibrations were extracted from three published studies. 4,445 children from Brazil and Taiwan between the ages of 0 to 77 months with similar percentages of males and females were included. Majority were typically developing children with 655 having atypical development due to a variety of medical conditions.

Intervention: None MAIN OUTCOME MEASURES: Gross Motor Units (GMU) and observed item difficulty calibrations for items on the Peabody Developmental Motor Scales-2 locomotor and stationary subscales and the Denver II gross motor subscale.

Results: There was a strong linear association between observed item difficulty for a sample of children with typical development and a mixed sample of typical and atypical development for the PDMS-2 locomotor and stationary subscales, respectively (locomotor subscale, disattenuated r = 0.97; stationary subscale, disattenuated r = 0.98). GMUs had strong linear associations with observed difficulty for items on the PDMS-2 locomotor and stationary subscales (disattenuated r = 0.88-1.00) for each scale when correcting for measurement error. A similar linear association was found between GMUs and observed difficulty for items on the Denver II gross motor subscale (r = 0.90).

Conclusions: The results of this study found that GMUs have a strong linear association with observed difficulty for gross motor development items from the PDMS-2 locomotor and stationary subscales and Denver II gross motor subscale. The strong association between observed item difficulties for children with typical and atypical development, across multiple scales suggests the GMU and construct specification equation can provide a means for consolidating all gross motor development items onto the same scale.