This chapter introduces the EQ-5D-5L questionnaire and its development by the EuroQol Group. The availability of the EQ-5D-5L, and the growing evidence of its pivotal role as a measurement system, generated a demand for ‘values’ to accompany it that would enable the use of EQ-5D-5L data in the estimation of quality-adjusted life-years (QALYs) and other applications where EQ-5D-5L profile data needs to be summarised by a single number. Chapter 1 sets out the main aim of the book: to provide an accessible source of information and guidance to support users of EQ-5D-5L and its value sets. Specifically, the book aims to improve users’ understanding of how EQ-5D-5L value sets are generated using the internationally standardised EQ-VT protocol; to raise awareness of the characteristics and properties of value sets; and to inform users’ choice of which value set to select for which purpose, and how that choice may affect analysis. The chapter concludes with an overview of the content of the book.
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