From translation to version management: a history and review of methods for the cultural adaptation of the EuroQol five-dimensional questionnaire.

The EuroQol five-dimensional (EQ-5D) questionnaire is used worldwide as a patient-reported outcome (PRO) instrument for the measurement and valuation of health. Several variants of the instrument now exist, including versions with three and five levels of severity and one for respondents aged 8 to 14 years. From the outset, a demand for new language versions of the EQ-5D questionnaire meant that there was a need to implement standardized procedures, which ensured that such versions were produced following international recommendations for the cultural adaptation of patient-reported outcomes. The availability of new variants and formats of the instrument, such as telephone-administered or electronic formats, complicated the task of providing and controlling the quality of cultural adaptations. Although cultural adaptations of the instrument are widely used, the procedures currently used to produce them have not been widely disseminated. The present article therefore describes the evolution of the production of other language versions of the instrument from the earliest days of simultaneous production and translation of the EQ-5D questionnaire to the more recent, broader-based strategy of version management. We describe current adaptation procedures and innovations within those procedures. We also describe how version management is organized within the EuroQol Group, review aspects related to quality control, and provide an overview of the number of currently available language versions for each variant of the EQ-5D questionnaire: three-level, five-level, and youth versions. We conclude by discussing some of the relevant issues related to cultural adaptation for frequently used instruments such as the EQ-5D questionnaire.