Background: The Gross Motor Function Measure (GMFM-88) is commonly used in the evaluation of gross motor function in children with cerebral palsy (CP). The relative reliability of GMFM-88 has been assessed in children with CP. However, little information is available regarding the absolute reliability or responsiveness of GMFM-88.
Objective: The purpose of this study was to determine the absolute and relative reliability and the responsiveness of the GMFM-88 in evaluating gross motor function in children with CP.
Design: A clinical measurement design was used.
Methods: Ten raters scored the GMFM-88 in 84 children (mean age=3.7 years, SD=1.9, range=10 months to 9 years 9 months) from video records across all Gross Motor Function Classification System (GMFCS) levels to establish interrater reliability. Two raters participated to assess intrarater reliability. Responsiveness was determined from 3 additional assessments after the baseline assessment. The interrater and intrarater intraclass correlation coefficients (ICCs) with 95% confidence intervals, standard error of measurement (SEM), smallest real difference (SRD), effect size (ES), and standardized response mean (SRM) were calculated.
Results: The relative reliability of the GMFM was excellent (ICCs=.952-1.000). The SEM and SRD for total score of the GMFM were acceptable (1.60 and 3.14, respectively). Additionally, the ES and SRM of the dimension goal scores increased gradually in the 3 follow-up assessments (GMFCS levels I and II: ES=0.5, 0.6, and 0.8 and SRM=1.3, 1.8, and 2.0; GMFCS levels III-V: ES=0.4, 0.7, and 0.9 and SRM=1.5, 1.7, and 2.0).
Limitations: Children over 10 years of age with CP were not included in this study, so the results should not be generalized to all children with CP.
Conclusions: Both the reliability and the responsiveness of the GMFM-88 are reasonable for measuring gross motor function in children with CP.