Gross Motor Function Measure-66 Item Sets for Use with Infants and Toddlers at High Risk for Cerebral Palsy: Construct Validity and Responsiveness

Authors

• Natalie A. Koziol, University of Nebraska-LincolnFollow
• Christiana D. Butera, University of Southern California
• Lin-Ya Hsu, University of Washington - Seattle Campus
• Silvana Alves Pereira, University of Rio Grande Do Norte
• Stacey C. Dusing, University of Southern California

ORCID IDs

Koziol https://orcid.org/0000-0003-3275-1776

Dusing https://orcid.org/0000-0003-3847-3893

Document Type

Article

Date of this Version

2025

Citation

Developmental Medicine and Child Neurology (2025) 67: 1063–1074

doi: 10.1111/dmcn.16259

Comments

Open access

License: CC BY-NC-ND 4.0

Abstract

To evaluate the construct validity and responsiveness of the Gross Motor Function Measure-66 Item Set (GMFM-66-IS), a standardized criterion-referenced observational measure, for use with children younger than 24 months with or at high risk for cerebral palsy (CP).

Non-experimental integrative data analysis was performed on secondary data from three clinical trials involving children with or at high risk for CP (n = 79, 42 males, mean corrected age = 11.3 months [SD = 4.9]), and one observational study of typically developing children (n = 32, 14 males, mean age = 5.7 months [SD = 0.8]). The GMFM-66-IS and comparator instrument (gross motor subtest from the Bayley Scales of Infant and Toddler Development, Third Edition [Bayley-III] or Bayley Scales of Infant and Toddler Development, Fourth Edition [Bayley-4], depending on the study) were administered at baseline and 3 months later. Comparator groups were based on neurological impairment, clinical rating of gross motor change, and CP status. Correlations (r) and regression-adjusted standardized mean differences (Hedges' g) were computed.

GMFM-66-IS and Bayley scores were correlated at baseline (r = 0.83), 3 months later (r = 0.88), and across time (r = 0.83). Children with mild impairment had higher mean GMFM-66-IS scores at baseline (g = 0.87) and 3 months later (g = 0.95). Children rated as demonstrating greater than expected gross motor change had larger mean GMFM-66-IS change scores than children demonstrating less than expected change (g = 0.62). Typically developing children had larger mean GMFM-66-IS change scores (g = 1.00).

GMFM-66-IS scores were supported by evidence of strong construct validity and moderate responsiveness.