Evaluating health-related quality-of-life studies in paediatric populations: some conceptual, methodological and developmental considerations and recent applications.

Although numerous paediatric-based health-related quality-of-life (HR-QOL) instruments are currently in use, there still remain conceptual, methodological and developmental issues to address. This paper provides an up-to-date critical review of the HR-QOL literature in paediatric medicine. Our analysis indicates that there is no consensus on how HR-QOL and overall QOL should be defined and measured in children. It is recommended that future studies focus on operationalising and distinguishing these constructs from each other and from traditional health-status measures. A clear empirical basis for generating instrument items and for prioritising specific domains must be described. Researchers should consider using the data gathered during their first interviews as a springboard from which to test their ideas of HR-QOL and QOL, reformulate concepts and subsequently retest their notions before developing instruments. Related to methodological challenges, consistency and agreement are still used interchangeably when comparing child and parent reports of children's HR-QOL. The Pearson correlation is a measure of co-variation in scores, and not a measure of agreement. We recommend that researchers focus on determining agreement as opposed to consistency. Few, if any, attempts have been made to account for the possibility that a response shift may have occurred in the evaluation of HR-QOL. Most studies have compared HR-QOL scores of children with illness with their healthy peers. As such, there is a dearth of knowledge regarding the normative process of adaptation within the context of illness. It is recommended that researchers focus on gathering data using a relative standard of comparison. We further recommend that researchers interpret HR-QOL data in line with their intended purpose. Regarding developmental consideration, particular attention ought to be paid to developing instruments that consider children's emerging sense of self, cognitive capacity and emotional awareness. Instruments that include items that are age appropriate are more likely to maximise reliability and validity of reports. The results of many HR-QOL instruments are applied in pharmacotherapeutic and pharmacoeconomic assessments. However, there has been relative infrequent application of economically valid HR-QOL tools (utility scales) and the use of HR-QOL scales as outcome measures in paediatric drug trials. As such, few cost-utility analyses have been performed to inform paediatric decision making. In addition, many of the concerns in the development of HR-QOL instruments should also be applied to the utility scales such that they reflect adequately children's preferences for health states.