Minimal Detectable Difference and Meaningful Change for Children with Cerebral Palsy on the Pediatric Balance Scale.

Research Report
Population: Pediatric

Nancy Sue Darr, PT, DSc, NCS, Professor, Belmont University School of Physical Therapy, Belmont University

Mary Rose Franjoine, PT, DPT, MS, PCS, Associate Professor, Department of Physical Therapy, Daemen College

Brenda Young, PhD, Professor, Department of Natural Sciences, Daemen College

Keywords: Prediction

The Pediatric Balance Scale (PBS), a 14 item measure of functional balance for children, demonstrates excellent psychometric properties: test-retest (ICC2,1=0.923), interrater (ICC2,1=0.972), and inatrarater reliability (ICC2,1=0.895-0.998). Each item is scored on a 0 to 4 scale, with 56 total points. The PBS can be administered to children ages ≥ 2 years. By age 5 years, 80% of children with typical development (TD) score ≥ 53 and by age 7 years, 69% score 56. Although the PBS discriminates children with mild and moderate balance dysfunction (BD) from their peers with TD, the minimal detectable difference (MDD) and the minimal clinical important change (MCIC) have not been established. The purpose of this study was to examine PBS MDD and identify meaningful change in children with cerebral palsy (CP).

Subjects: MDD was calculated via retrospective analysis of 825 healthy children, 2 to 13 years. Subjects included 687 children with TD and 138 children with BD. Meaningful change was examined via analyses of data from a longitudinal study of 36 children with CP, ages 5 to 14 years. The PBS was administered to these children triannually up to 3 years. At each testing session the child, parent, and treating therapist (CPT) each rated the child’s balance on a Likert Scale of 1 to 5, and assistive devices (AD) used for mobility were recorded.

Methods: MDD was calculated for the entire sample of 825 children and by age in one-year increments using the formula: MDD95 = 1.96 * SEM * √2
Meaningful change was examined with correlations (rs) between PBS scores, CPT perceptions of balance, and assistive device(s) used for mobility for each child. Relationships between changes in PBS scores, CPT perceptions and AD use were also examined using scatterplots and correlations (rs).

Results: MDD was 4.7 for the entire sample of children, and ranged from 6.1 in 2 year olds, to 4.5 in 3 and 4 year olds with subsequent decreases by age group to ≤ 1.308 in children ≥ 8 years.  Except for children with PBS scores > 52 throughout the duration of the study, correlations between PBS scores and CPT perceptions of balance were strong (rs = 0.557 to 0.993). Correlations were strong between changes in PBS scores and changes in CPT perceptions (rs = .735 to .871) and between changes in PBS scores and changes in AD (rs = .869). PBS scores were < 24 when a wheelchair was used for mobility and > 32 if the child walked independently without an AD. PBS scores for children who primarily ambulated with an AD ranged from 13 to 48. PBS scores for this sample of 36 children with CP were lower than what one would expect in children with TD (mean = 36.27±14.52).

Conclusions and Clinical Relevance:  The MDD for the PBS varies by age from 6 points in 2 years olds to 1 point in children, ages 8 and older. Changes in PBS scores correlate with changes in PCT perceptions of balance in children with CP and changes in AD use. Children with CP, ages 5 and older, who score less than 24 on the PBS may likely use a wheelchair for most mobility.

Darr, Nancy Sue, PT, DSc, NCS; Franjoine, Mary Rose , PT, DPT, MS, PCS; Young, Brenda , PhD. Minimal Detectable Difference and Meaningful Change for Children with Cerebral Palsy on the Pediatric Balance Scale.. Poster Presentation. IV STEP Conference, American Physical Therapy Association, Columbus, OH, July 17, 2016. Online.