The 2011 Oxford CEBM Levels of Evidence: Introductory Document
The 2011 Oxford Centre for Evidence-Based Medicine’s Levels of Evidence.Key Concepts addressed:
What the 2011 OCEBM Levels of Evidence Is
- A hierarchy of the likely best evidence.
- Designed so that it can be used as a short-cut for busy clinicians, researchers, or patients to find the likely best evidence. To illustrate you may find the following analogy useful (Figure 1). Imagine making a decision about treatment benefits in ‘real time’ (a few minutes, or at most a few hours). There are five boxes each containing a different type of evidence: which box would you open first? For treatment benefits and harms, systematic reviews of randomized trials have been shown to provide the most reliable answers (1), suggesting we begin by searching for systematic reviews of randomized trials. If we didn’t find any evidence in the systematic review box, you would go onto search for individual randomized trials, and so on across the OCEBM Levels of Evidence.