Measurement of health status, functional status, and quality of life in children with juvenile idiopathic arthritis: Clinical science for the pediatrician

The historical focus in assessment of children with juvenile idiopathic arthritis (JIA) [I] has been on hard outcomes such as persistent disease activity, disease remission, joint damage, and organ system damage. A number of the measures of these outcomes have been grouped as a core set and used to define improvement in JIA [2]. These outcomes are important and need to be measured. JIA, however, like most other chronic diseases of childhood, influences virtually all aspects of the child's life, including physical, social, emotional, intellectual, and economic aspects, and affects the entire family with ultimate effects on the child's overall outcome [3,4]. Thus, there is also a need for a more all-encompassing picture of the health status, functional status, socioeconomic status, and quality of life (QoL) of these children. Unfortunately, the terminology in this area can be confusing, because the terms health status, functional status, and QoL are frequently used interchangeably. Thus they merit definition. Health status is an overall point estimate of a person's well being in physical, psychologic, and social terms compared with some baseline assessment. Functional status is a broad summary statement with respect to the effect of a disease on the patient's ability to carry out usual tasks, such as the activities of daily living. QoL includes both health status and functional status. Moreover, measurement of QoL should attempt to incorporate some aspect of the patient's own perception of which aspects of his/her life are significantly affected and the extent to which this perception is influenced by the disease [5]. QoL measures used in the clinical domain tend to focus on health-related quality of life (HRQoL). All such measures may be divided into generic and disease-specific measures [6]. Generic measures have broad application across different types and severity of disease, across different treatments, and across cultural subgroups. Disease-specific measures are designed to assess specific diseases or patient populations and, as such, are usually more responsive to changes in the status of the individual subject. Considerable work has been conducted in JIA in the past 15 years to develop new measures, including functional status and HRQoL measures, in an effort to define better the overall outcomes for these children. Comprehensive reviews provide a more detailed discussion of these issues [7-9]. This article focuses on the general process of measure development, some of the specific measures developed for JIA, and their use in defining patient outcomes.