Levels of evidence and study designs: A brief introduction to dermato-epidemiologic research methodology

Levels of evidence (LOE), also known as hierarchies of evidence, are determined primarily by the inherent bias and validity of the study designs. Understanding LOE is a crucial preliminary step in practicing evidence-based medicine (EBM) or evidence-based dermatology. These hierarchies facilitate the efficient acquisition of the best available evidence for clinicians in decision-making, as well as guiding researchers in conducting new studies with appropriate designs while considering the next higher LOE necessary to improve the quality of currently available evidence. This article provides a concise overview of LOE and study designs based on the 2011 Oxford Centre for Evidence-Based Medicine LOE for treatment benefits. We utilize examples from medical literature to elucidate the strengths and limitations of various study designs. Furthermore, we shed light on the key concepts of the updated evidence pyramid and how the EBM research roadmap functions to bridge the gap between current best evidence and clinical practice.