Implicit factors can be defined as any criteria that play a role in the health technology assessment (HTA) deliberative process but are not part of the HTA framework. To date, very few studies have explored the influence of implicit factors on this process. This survey of HTA experts in five European countries aimed to analyze the influence of implicit factors on the HTA deliberative process.

Semi-structured interviews with 20 HTA experts from five European countries (France, Germany, Italy, Spain, and the United Kingdom) were conducted from February to May 2021. The main topics of the interviews were: the HTA deliberative process; the degree of influence on the HTA deliberative process of a set of factors previously identified in a systematic literature review performed by the authors; and recommendations for improving the deliberative process.

All but two of the experts concurred that implicit factors played a role in the deliberative process. German experts considered that the factors explored had a low influence on the process. Burden of disease and unmet need scored highest, followed by the professional experience of the people involved in the HTA deliberative process. To improve the deliberative process, experts suggested expanding the external stakeholder perspective (i.e., including patients, the pharmaceutical industry, and the public), increasing transparency when revealing implicit factors, and implementing a methodology to mitigate the influence of implicit factors.

Our survey indicates a need to increase external involvement in the process and to develop a methodology for unmasking the implicit factors in the deliberative process. This may be achieved by either updating the current frameworks to include these implicit factors or by developing new methods to address them. Further research may explore approaches to acknowledge the implicit factors in the HTA deliberative process in a systematic manner.