Health status (arthritis impact) in children with chronic rheumatic diseases. Current measurement issues and an approach to instrument design.

Arthritis outcome measures in adults have evolved from biologic "disease activity," to observations of motor/movement based "functional status," to assessment of "health status." This monograph suggests a framework for developing a pediatric arthritis health status (impact) instrument in which measurable global outcome dimensions include psychological, social, ADL, pain, school, family, behavioral, and developmental variables. Physical and laboratory parameters of inflammation/disease activity are not part of either functional status or arthritis impact, but rather perhaps the most important predictor variable of outcome. Juvenile rheumatoid arthritis (JRA) is a prototypic chronic disease for development of a health status instrument for children. Prior obstacles have been (a) that systemic, polyarticular, and pauciarticular JRA appear to have very different amounts of impact on health status; and (b) although juvenile arthritis has proven a useful term for medical and public education, its value as a study entry criterion for functional status instrument development is limited. Any new pediatric arthritis impact instrument must fulfill five criteria: enable quantification; demonstrate reliability, validity, and precision; and specify data collection procedures. Important design issues include (a) developing a self-report format for children, (b) ensuring generalizability across age groups, and (c) the parent as proxy in most patient-related dialogue and interventions. Instrument elements could come from 8-10 adult and pediatric health/functional status instruments already in use. By 10 years of age, children can provide much independent information. Whether global assessments by patient, parent, and physician should be included, or be a separate "gold standard," is not yet clear. The creation of better health status measures is an important and formidable challenge for pediatric rheumatology.