Expert opinion on a consensus-based checklist for the critical appraisal of cost-of-illness (COI) studies: qualitative interviews.

Objectives: This study explored experts' views on the development of a proposed checklist for cost-of-illness (COI) studies. It also investigated experts' perspectives on the use of COI studies and quality/critical appraisal tools used for COI studies as well as their experiences with the use of these tools.

Methods: Semi-structured, open-ended interviews were conducted with health economists and other experts working with COI studies and with experience of developing health economic guidelines or checklists. Participants were selected purposively using network and snowball sampling. A framework approach was applied for the thematic data analysis. Findings were reported narratively.

Results: Twenty-one experts from eleven different countries were interviewed. COI studies were found to be relevant to estimate the overall burden of a disease, to draw attention to disease areas, to understand different cost components, to explain cost variability, to inform decision making, and to provide input for full economic evaluations. Experts reported a lack of a standardized critical appraisal tool for COI studies. Their experience related predominantly to guidelines and checklists designed for full economic evaluations to review and assess COI studies. The following themes emerged when discussing the checklist: (i) the need for a critical appraisal tool, (ii) format and practicality, (iii) assessing the questions, (iv) addressing subjectivity, and (v) guidance requirements.

Conclusions: The interviews provided relevant input for the development of a checklist for COI studies that could be used as a minimum standard and for international application. The interviews confirmed the important need for a checklist for the critical appraisal of COI studies.