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

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Abstract
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.