Research pearls: how do we establish the level of evidence?

Evidence-based medicine (EBM) guidelines were first introduced in 1986 and were defined as the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. The practice of EBM means integrating individual clinical expertise with the best available external clinical evidence from systematic research. Level of evidence (LOE) stratifies publications from Level I to Level V and provides the foundation for EBM. Three questions should be asked when an LOE is assigned to a scientific article: (1) What is the research question? (2) What is the study type? and (3) What is the hierarchy of evidence? In cases in which LOE is not appropriate or relevant (basic science and laboratory-based investigations), a clinical relevance statement should be used. Unfortunately, study quality is not assessed by the assigned hierarchy level. LOE and EBM have increased the number of investigations published with better levels of evidence. As authors, reviewers, editors, and publishers, we desire a system that is consistent, effective, and reliable. Fortunately, the system has proven to have all of those attributes with good interobserver and intra-observer values. The increase in investigations with higher LOEs allows for more frequent use of EBM