Also the concept of ‘‘validity’’ of QoL instruments has
been particularly difficult to define and measure due to the
lack of an agreed and objective gold standard of QoL.
Current approaches suggest the employment of quantitative
(e.g. factor analysis) and qualitative (e.g. patient debriefing
questionnaires and patient panels) techniques. While these
procedures have been increasingly used in the development
of instruments to measure QoL in children and young
people the process has not yet been repeated in different
patient groups. And in particular there has been little work
conducted to demonstrate validity in children with mental
health problems.