Clinical epidemiology for comprehensive kidney care: a framework for developing clinical research questions, from biomarkers to patient-reported outcomes.

Clinical nephrology research is increasingly challenged by the need to translate complex patient experiences, emerging biomarkers and treatments, and an expanding methodological tools into improvements in care. Clinical epidemiology provides a bridge between bedside questions and population science; however, its role is often narrowly perceived as clinical statistics rather than as a discipline centered on research conceptualization and design. In this invited review, I reflect on how clinical questions arising from routine nephrology practice can be systematically developed into clinically relevant research through a nephrologist-epidemiologist's lens. First, drawing on our experience and illustrative examples, I describe how rethinking care processes through established frameworks-such as the structure-process-outcome model-can support clinicians in formulating answerable questions that matter to patients. Second, I expand the lens beyond traditional nephrology to incorporate perspectives from social medicine, emphasizing trust, hope, and patient-reported outcomes as integral components of chronic kidney disease care. Finally, this review highlights how clinical questions can be embedded within clinical research design frameworks to clarify research objectives across diagnosis, treatment, prognosis, and etiology. In an era of rapid methodological diversification, the nephrologist-epidemiologist's unique contribution may lie in cultivating a sharpened lens: the ability to discern relevant clinical questions and sustain deep clinical reasoning. By doing so, clinical epidemiology can continue to guide research that advances comprehensive and patient-centered kidney care.