Measuring pediatric patient-reported outcomes: good progress but a long way to go

The pre-Socratic Greek philosopher Protagoras (490 BC– 420 BC) made an argument about 2,500 years ago: Man is the measure of all things—of things which are, how they are, and of things which are not, how they are not [1]. This controversial idea is in contrast with a long-standing paradigm claiming that the universe is based on objective matters and outside the human’s subjective influence. Similarly, the use of objective methods such as laboratory tests and diagnostic imaging rather than subjective and self-reported methods to evaluate patient health outcomes has dominated medical sciences for several 100 years. Although clinicians and policy makers have gradually accepted the notions ‘‘quality of life (QOL),’’ ‘‘healthrelated quality of life (HRQOL),’’ or ‘‘patient-reported outcomes (PROs)’’ as an endpoint in the adult setting, the pediatric setting has lagged behind in considering selfreports in concept initiation, instrument development, and clinical application of PROs. We conventionally believed that children’s self-reported health information is unreliable and together with complex developmental issues, resulted in insufficient attention to and under-utilization of pediatric PRO data. Indeed, children are able to report their health status in an adequate manner [2], and pediatric PRO instruments need to carefully accommodate specific content related to children’s cognitive development as well as reading ability, vocabulary, and language skill. This special section of Quality of Life Research includes four articles exclusively focusing on the theme of pediatric PROs. Two articles applied the International Classification of Functioning, Disability, and Health—Children and Youth Version (ICF-CY) as a framework to compare the conceptual content of pediatric PROs embedded in existing instruments for children and adolescents with chronic conditions [3, 4]. One article synthesized the constructs of PRO instruments for pediatric cancer [5], and another article summarized the development of the KIDSCREEN which is commonly used in European pediatric studies [6]. We applaud the authors for their efforts and useful findings in pediatric PRO measurement. The comparison among pediatric PRO instruments is a challenging task because these instruments were not created based on the same conceptual foundation. Instrument developers use different conceptual frameworks to generate target PROs with specific content and domains and employ various stakeholder-engagement processes to create items. They also apply different psychometric methods to evaluate PRO measures. Previous review articles on pediatric PRO instruments might be misleading because the comparison is confined to the ‘‘face value’’ of the instrument domains [7–9]. These studies often assumed that the domains named by individual instruments (e.g., physical functioning) reflected the genuine concepts of PROs, neglecting the actual content of the items embedded in each instrument. Consequently, the same domain name across different instruments does not necessarily mean they I.-C. Huang (&) D. A. Revicki Department of Health Outcomes and Policy, Institute for Child Health Policy, College of Medicine, University of Florida, PO Box 100177, Gainesville, FL 32610, USA e-mail: ichuang@ufl.edu