The introduction of the EQ-5D-5L offered an opportunity to develop a standardised valuation protocol, the EQ-VT protocol, with improved methods for health state valuation that enables comparison of the resulting value sets between countries. This chapter summarises the process of developing and strengthening the methods for valuing EQ-5D-5L in the EQ-VT protocol which underpins the valuation studies reported in this book. This includes an overview of the methodological research programme that informed the initial EQ-VT protocol and a description of the key elements of the protocol and the included valuation techniques, i.e. composite time trade-off and discrete choice experiments. This chapter also discusses the first wave of EQ-5D-5L valuation studies which used the protocol and the resulting conclusions; the subsequent modification and strengthening of the EQ-VT protocol including a quality control procedure; and experience with use of the improved EQ-VT protocol in the subsequent waves of EQ-5D-5L valuation studies. The chapter concludes with an overview of the lessons learned during this journey of evidence-based refinement of the EQ-VT protocol from version 1.0 to the current version 2.1.
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