Brief assessment of motor function - Reliability and concurrent validity of the Gross Motor Scale

Objective: The Brief Assessment of Motor Function (BAMF) is a series of 10-point ordinal scales developed for rapid description of gross motor, fine motor, and oral motor performance. We examined interrater and intrarater reliability and concurrent validity of the BAMF Gross Motor Scale. Design: This validation study included 48 children (age, 5 mo to 17 yr) with a wide range of gross motor capability. Ten children with varied diagnoses participated in the reliability study. For concurrent validity, the BAMF performance of 38 children with osteogenesis imperfecta was compared with scores on the Peabody Developmental Motor Scales, laboratory gait analysis, and manual muscle testing. Results: Reliability values for intraclass correlations were 0.996 (interrater) and 1.00 (intrarater). Significant relationships were identified between the BAMF and gait speed (r=0.68, P<0.0001), stride length (r=0.71, P<0.0001), duration of double-limb support (r=-0.40, P<0.03), number of weak muscles (r=-0.74, P<0.0001), and the Peabody Developmental Motor Scales (r=0.95, P<0.0001). Number of weak muscles was the strongest predictor of BAMF score (R-2=0.5080, F=24.77, P<0.0001). Conclusions: The BAMF demonstrates good reliability for children with a range of diagnoses and acceptable concurrent validity with gross motor development, muscle strength, and formal gait assessment in children with osteogenesis imperfecta.