Gross Motor Function Measure‐66 Item Sets for use with infants and toddlers at high risk for cerebral palsy: Construct validity and responsiveness
Aim
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).
Method
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.
Results
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).
Interpretation
GMFM‐66‐IS scores were supported by evidence of strong construct validity and moderate responsiveness.
