The participation of lifeworld experts in Delphi processes: A reflection on method and practice.

Delphi studies have established themselves in the health sciences as a means to systematically and, ideally, synthesize expert opinions into a consensus on concrete issues. As participatory health research increases in relevance, lifeworld experts (e.g., patients, caregiving relatives) are being included in Delphi surveys and their opinions placed alongside those of professional and scientific experts. Looking at the theory and methodology, we discuss the opportunities and challenges concerning result quality and derive practical implications for conducting Delphi studies involving lifeworld experts alongside scientific and/or professional experts. Delphi techniques are understood here to be social interaction processes whose outcomes are a result of the participating experts' conscious, cognitive judgment processes, and also shaped by individual, situational and cultural factors. The more heterogeneous the expert panel, in particular when lifeworld experts are participating, the more these influences vary. Expert panel composition and how diversity is handled prove significant to Delphi study results. Our argument is based on an in-depth analysis of a systematic review of Delphi studies with lifeworld experts. We found that the inclusion of lifeworld experts in Delphi studies usually occurs relatively unsystematically and, furthermore, that results are not analysed separately according to expert group, although there would be good reasons for this. We have oriented the reporting here on PRISMA. To enhance the outcomes of Delphi studies that incorporate lifeworld experts alongside scientific and/or professional experts, we put forward specific recommendations that address potential biases arising from the participation of lifeworld experts.