Introduction
Health-related quality of life (HRQoL) is seen as an increasingly important outcome in clinical, epidemiological, and health economics studies in children and young people [The PedsQL is a generic non-preference-based instrument for use in children and adolescents [Preference-based measures such as the CHU9D tend to be less often used in clinical studies [A methodological challenge of the mapping algorithms is to ensure consistency in their predictive accuracy across population subgroups. Existing algorithms have been developed using populations with limited age ranges and medical conditions [We aim to externally validate the most recent PedsQL to CHU9D mappings for a sample of children and young people of a wide age range (0 to 16 years of age) and with chronic conditions, from an ethnically diverse and deprived area in South London. In addition, we assess whether new algorithms could improve the predictive accuracy for this unique population.