Objectives: The use of unvalidated resource-use measurement (RUM) instruments gives way for inaccurate resource-use estimates in economic evaluations. The involvement of a broader range of stakeholders, among which potential respondents (patients or caregivers), is therefore an essential part of the development of a RUM instrument. Their experiences can be included by employing qualitative methods as think-aloud interviews, enabling researchers to gain insight into the thinking processes. With the absence of a gold standard and of appropriate guidelines on the use of think-aloud interviews in health economics, these methods remain relatively unknown. Therefore, this study aims to describe a manual for applying think-aloud interviews in the process of developing the PECUNIA RUM instrument, which aims to capture individual generic resource use from a societal perspective.

Methods: The manual was developed by an international working group of health economists with expertise in RUM. Relevant information on think-aloud methods in health economics was gathered via snowballing literature searches and additional external expertise was sought. The manual aims to harmonize the think-aloud interviews in four countries (Germany, Netherlands, Austria, and the UK) by describing the recruitment of participants and the execution of the interviews. The recruitment phase describes whom to recruit, how to recruit, and the necessary participant information provision. The execution phase describes the structure of the think-aloud interviews and provides hands-on information for interviewers. This phase is split into online and face-to-face settings, to enable researchers to operate in compliance with national and institutional policies.

Discussion: This study is part of the PECUNIA project and aims to harmonize multi-national think-aloud interviews for pilot-testing the PECUNIA RUM instrument. As qualitative methods have not been widely used in health-economics, it adds value by increasing transparency in applied qualitative health economics research. The manual can be easily adapted to serve other think-aloud studies as well.