Abstract
OBJECTIVE: To present a radically interdisciplinary research approach to ill-defined symptoms, with a focus on fatigue as a major symptom of post COVID-19 condition, where multiple and, to date, rarely combined approaches may yield a fuller understanding of these symptoms. DESIGN: Protocol for a mixed-methods study comprising an interdisciplinary cross-analysis. PATIENTS: 35 persons with post COVID-19 condition and severe fatigue were included, and 35 age-, sex-, and educationally matched controls who recovered from COVID-19 without post COVID-19 condition. METHODS: Participants were assessed by a multidisciplinary research team as follows: physician assessment; blood and urinalysis; spirometry and physical performance tests; neuropsychological tests; structural and functional magnetic resonance imaging; extended immunological tests (cytokines); and qualitative phenomenological analysis of interviews. Data will be analysed in accordance with established methods in each of these research fields and by a cross-analysis methodology developed from within an enactive framework. This framework encompasses a focus on neuroscientific, physiological, and experiential aspects of the person as a living being in their sociocultural world. CONCLUSION: The biopsychosocial model needs to be implemented in research according to methods that allow radically different research paradigms, typically seen as incommensurable, to inform each other in a non-reductionist manner. One application of such an approach is therefore described.