Children with a rheumatic disease frequently experience impairments in one or more body systems; these may include pain, stiffness, fatigue, muscle weakness, soft tissue contractures, and poor exercise capacity. These impairments may directly limit the child's ability to perform some physical activities or may do so indirectly if the child or parent fears such activities may cause injury or a disease flare. It is essential to understand the impact of rheumatic disease on a child's activities in order to guide intervention and monitor changes in functional abilities over time and with targeted therapies. This is especially important when disease onset occurs at a very young age because the long-term effects of physical limitations can negatively impact the child's quality of life.
The best measure of activities for a particular child or group of children depends on the context of the evaluation, including the physical and social environment. For example, a child may perform a task like standing up from the floor without assistance in a quiet, standardized environment like the clinic, but does not perform the same task during physical education class at school or after a fall in the community. Holsbeeke et al (1) suggest there are 3 related but separate constructs of physical activity that are distinguished by this person-environment interaction. Capacity describes what a person can do in a standardized controlled environment, capability describes what a person can do in his/her daily environment, and performance describes what a person actually does in his/her daily environment.
Four measures of physical activities that have been developed for or are appropriate for use in children with a rheumatic disease will be reviewed. Only the Juvenile Arthritis Functional Assessment Scale (JAFAS) and the Childhood Health Assessment questionnaire (C-HAQ) were developed specifically for children with juvenile arthritis. The C-HAQ, the most frequently used measure of activities in pediatric rheumatology, evaluates a child's capability to perform activities in their daily environment, while the JAFAS measures the child's capacity in the daily environment. Both the Activities Scale for Kids (ASK) and the Pediatric Outcomes Data Collection Instruments (PODCI), although not specifically designed for use in pediatric rheumatic diseases, assess physical function in children with chronic health disorders, including childhood arthritis. The ASK includes 2 versions, one that measures a child's physical capability in his/her daily environment (ASKc) and one that measures the child's performance of the same activities in their daily environment (ASKp). The ASK is also the only measure that requires the child to be the respondent because, as Young et al (2) state, “it is the child who is most familiar with his or her own abilities or limitations in each setting.” Finally, the PODCI, the most comprehensive of the 4 instruments, measures capability primarily, and includes a pediatric version to be completed by a parent and an adolescent version that can be completed by the parent, child, or both. Each of these 4 measures includes activities that are necessary and important to children across a wide age range. The use of 2 or more of these measures in combination may provide clinicians with the best understanding of a child's typical activities and participation in age-appropriate settings.