Psychometric Evaluation of 2 New Upper Extremity Functional Strength Tests in Children With Cerebral Palsy

Abstract

Background For children with unilateral spastic cerebral palsy (USCP), reduced muscle strength may lead to activity limitations. However, despite existence of many upper limb strength measures, none measure strength in the context of functional activities in which the strength must be maintained for several seconds.

Objective The objective was to evaluate the psychometric properties of two newly developed functional hand and upper limb muscle-strength tests (Cup- and Box task) in children (7–12 years) with USCP.

Design A longitudinal study design was used.

Methods A standardized protocol with detailed descriptions of all procedures and measurements was used to determine test-retest reliability, inter-rater reliability, and criterion validity.

Results A total of 86 children (53 males, 33 females, mean age = 9.3 years) with USCP participated in this study, with a subset performing each measurement. Only the results of the children who are able to perform the measurement were included for the analysis. Excellent test-retest reliability (Intraclass correlation coefficients (ICC) ranging from 0.887 to 0.944; 95% confidence intervals 0.713–0.969) and inter-rater reliability (ICC ranging from 0.896–0.960; 95% confidence intervals 0.813–0.980) was observed. The Cup-Task Affected-Hand and Box-Task were moderately correlated with maximum isometric grip strength. The Cup-Task Non-Affected-Hand had a low correlation with maximum isometric grip strength.

Limitations Age, gender, and manual ability were not normally distributed, which could have influenced the results.

Conclusions For children with USCP who can perform the tasks, the Cup- and Box-Task are reliable and valid instruments for measuring functional upper limb muscle strength.