Reliability of the selective motor control scale in children with cerebral palsy

The aim of this study was to determine inter-rater and test–retest reliability of a scale for assessing selective motor control (SMC) in the dorsiflexors of the ankle. A consecutive sample of 40 children with cerebral palsy (CP), aged 3–16 years (median age 7 years) participated in the study. Thirty children had a bilateral form of CP and 10 a unilateral form, and they were classified into Gross Motor Function Classification System levels I–V. The SMC scale ranges from 0 (indicating no ankle movement) to 4 (indicating isolated SMC through available range of motion with balanced activity in m. tibialis anterior). The inter-rater reliability was assessed simultaneously by three assessors. The test–retest reliability was achieved through a second assessment of 29 of the children, at a different occasion. The statistical analysis included a weighted kappa coefficient of agreement (Kw). The inter-rater reliability showed fair/good to strong agreement between pairs of raters (Kw=0.58–0.77). The test–retest reliability was strong (Kw=0.88–1). Since the inter-rater reliability varied between fair/good to strong and the test–retest reliability was strong, we conclude that repeated evaluations should preferably be performed by the same rater.