Construct Validity of a Task-Oriented Bimanual and Unimanual Strength Measurement in Children With Unilateral Cerebral Palsy

OBJECTIVE: The purposes of this study were to (1) investigate aspects of construct validity of peak force measurements of crate-and-pitcher tasks using the Task-oriented Arm-hAnd Capacity (TAAC), an instrument designed to measure task-oriented arm and hand strength for cross-sectional and evaluation purposes, and (2) compare TAAC measurements with those of comparative measures using COSMIN guidelines. METHODS: In this cross-sectional validity study, participants were 105 children (mean age = 12 years 10 months; number of boys = 66) diagnosed with unilateral cerebral palsy (UCP). Ten a priori hypotheses were formulated with peak force of the TAAC as index measure and compared with measures on body functions and structure and activity level of the International Classification of Functioning, Disability and Health for Children and Youth. Strength and direction of the relationship between the TAAC and comparative measures were investigated by calculating Pearson correlation coefficients (r). RESULTS: On body functions and structures level, low-to-moderate positive correlations (0.493–0.687) were found. On activity level, low negative and positive correlations (−0.271 to 0.387) were found. CONCLUSION: The construct of peak force measurement of the TAAC is in line with the a priori hypotheses with comparators on body function and structures and activity level, indicating a partial overlap of the construct of the TAAC with both International Classification of Functioning levels. The TAAC appears to be valuable, as it measures functional strength that differs from the constructs of the comparators. More research with a larger population and more comparators is needed. IMPACT: Clinically relevant information is lacking about the use of strength and strength measurement during daily activities in children with UCP. This study shows that the TAAC provides unique information about functional strength in children with UCP.