Detecting individual change in children with mild to moderate motor impairment: the standard error of measurement of the Movement ABC.

OBJECTIVE To assess whether the Movement ABC can be used to monitor individual change in motor performance. DESIGN Motor-impaired children were tested three times in succession with the Movement ABC without any intervention. SETTING Two schools for special education and one school for children who are chronically ill. SUBJECTS Three girls and 20 boys aged 6-8 years. MAIN OUTCOME MEASURES Scores were measured per item (0 --> 5), added to cluster scores (0 --> 10 or 15), added to form the total scores (0 --> 40). Mean scores, standard errors of measurement (SEMs) and least detectable differences (LDDs) were calculated per item, per cluster and for the total scores. A repeated measures analysis of variance was performed to test for the effects of time. RESULTS The total scores improved significantly from the first session (mean: 15.4 points) to the second (mean: 13.3), but not from the second to the third (mean: 13.2). Average item scores ranged from 0.6 to 2.7 points with SEMs of 0.79 --> 1.54 and LDDs of 2.20 --> 4.27. Average cluster scores ranged from 3.4 to 5.3 with SEMs of 1.51 --> 1.84 and LDDs of 4.18 --> 5.11. The SEM of the total scores equalled 3.13 with an LDD of 8.68. CONCLUSIONS The total score of the Movement ABC is sufficiently sensitive to monitor individual change; the cluster scores have moderate sensitivity and individual items are inappropriate to monitor individual change. The significant effect of time is interpreted as an effect of learning.