Hierarchy of Evidence Within the Medical Literature

The quality of evidence from medical research is partially deemed by the hierarchy of study designs. On the lowest level, the hierarchy of study designs begins with animal and translational studies and expert opinion, and then ascends to descriptive case reports or case series, followed by analytic observational designs such as cohort studies, then randomized controlled trials, and finally systematic reviews and meta-analyses as the highest quality evidence. This hierarchy of evidence in the medical literature is a foundational concept for pediatric hospitalists, given its relevance to key steps of evidence-based practice, including efficient literature searches and prioritization of the highest-quality designs for critical appraisal, to address clinical questions. Consideration of the hierarchy of evidence can also aid researchers in designing new studies by helping them determine the next level of evidence needed to improve upon the quality of currently available evidence. Although the concept of the hierarchy of evidence should be taken into consideration for clinical and research purposes, it is important to put this into context of individual study limitations through meticulous critical appraisal of individual articles.