Exploring the Comparability of Face-to-Face Versus Video Conference-Based Composite Time Trade-Off Interviews: Insights from EQ-5D-Y-3L Valuation Studies in Belgium and Spain.

Background: Face-to-face interviews are recommended for the collection of composite time trade-off (cTTO) data. The coronavirus disease 2019 (COVID-19) social distancing measures made researchers consider videoconferencing interviews as an alternative mode of administration, but little evidence about the implementation of videoconferencing in valuation studies is available. This study provides insights into the effect of videoconferencing on the quality of data, evaluating interviewers' and respondents' engagement level in videoconferences compared with face-to-face interviews.

Methods: We used cTTO data collected in Belgium and Spain following the EQ-5D-Y-3L valuation protocol. Due to the COVID-19 pandemic, both projects interrupted the face-to-face data collection before reaching the target sample. The remaining interviews were conducted by videoconference. We compared both modes of administration in terms of interviewers' engagement (task duration and number of moves in each example) and respondents' engagement (task duration and proportions of specific response values, in half-year units). To minimise interviewers' learning effects, we split our sample into three groups: (1) first 20 interviews conducted face-to-face; (2) subsequent interviews conducted face-to-face; and (3) videoconferencing interviews.

Results: The comparison between videoconferencing and subsequent face-to-face interviews showed the interviewer's engagement was not affected by the mode of administration as almost no significant results were found either in the task duration or the numbers of moves shown in the examples. Similarly, none of the respondents' task duration or proportion of specific responses or half-year units were affected by the mode of administration in either of the two countries.

Conclusions: No evidence suggested that the quality of cTTO data is reduced when using videoconferencing compared with face-to-face interviews.