Designing qualitative research with value in the clinical and epidemiological context: what, why and how

Clinical and epidemiological research is indispensable for improvements in evidence-based healthcare and health outcomes, but it also leaves important gaps in our understanding of health and illness. Qualitative research has been increasingly recognized as a key to addressing some of these gaps, using both exploratory (to gain a more complete and in-depth understanding of problems) and explanatory (to explain quantitative results) approaches. By finding out 'what's going on' and bringing people's stories to light, qualitative research is widely advocated as crucial in enhancing patient-centered research and healthcare. To date, most clinicians, clinical researchers and epidemiologists are relatively unfamiliar with and untrained in qualitative research-a type of research that, compared with quantitative research, requires different research skills and uses a different jargon, type of reasoning, and methods. This article aims to equip them with the basic knowledge necessary to appraise and design qualitative research. Specifically, we provide a comprehensive overview of (i) what qualitative research is, including various examples of qualitative research questions and explanations of the contrasting properties of quantitative and qualitative research; (ii) what constitutes the added value of qualitative research in the clinical and epidemiological context, illustrated using numerous research studies conducted within nephrology; and (iii) practical guidelines for designing qualitative research within this context, including a self-developed checklist containing essential information to include in qualitative research protocols. In doing so, we hope to enrich clinical and epidemiological research with complementary qualitative evidence-amongst others, invaluable insights into patients' lived experiences and perceptions-and thereby greatly enhance patient-centered research and evidence-based healthcare.