Reliability of the modified Gross Motor Function Measure-88 (GMFM-88) for children with both Spastic Cerebral Palsy and Cerebral Visual Impairment: A preliminary study

• Cerebral Visual Impairment is observed in 30% of children with Cerebral Palsy.
• No reliable instruments exist to measure changes in motor function in these children.
• Therapists need an adapted test to measure motor function in these children.
• The GMFM-88-CVI is reliable to measure gross motor function.

PurposeThe aims of this study were to adapt the Gross Motor Function Measure-88 (GMFM-88) for children with Cerebral Palsy (CP) and Cerebral Visual Impairment (CVI) and to determine the test–retest and interobserver reliability of the adapted version.MethodSixteen paediatric physical therapists familiar with CVI participated in the adaptation process. The Delphi method was used to gain consensus among a panel of experts. Seventy-seven children with CP and CVI (44 boys and 33 girls, aged between 50 and 144 months) participated in this study. To assess test–retest and interobserver reliability, the GMFM-88 was administered twice within three weeks (Mean = 9 days, SD = 6 days) by trained paediatric physical therapists, one of whom was familiar with the child and one who wasn’t. Percentages of identical scores, Cronbach's alphas and intraclass correlation coefficients (ICC) were computed for each dimension level.ResultsAll experts agreed on the proposed adaptations of the GMFM-88 for children with CP and CVI. Test–retest reliability ICCs for dimension scores were between 0.94 and 1.00, mean percentages of identical scores between 29 and 71, and interobserver reliability ICCs of the adapted GMFM-88 were 0.99–1.00 for dimension scores. Mean percentages of identical scores varied between 53 and 91. Test–retest and interobserver reliability of the GMFM-88-CVI for children with CP and CVI was excellent. Internal consistency of dimension scores lay between 0.97 and 1.00.ConclusionThe psychometric properties of the adapted GMFM-88 for children with CP and CVI are reliable and comparable to the original GMFM-88.