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Level of evidence base on study design
EBM has a hierarchy of strength of evidence for treatment decisions. The hierarchy of evidence is a spectrum of potential sources beginning with those most likely to provide the evidence to those with the least likely. based on the methodological quality of their design, validity, and applicability to patient care. These decisions give the "grade (or strength) of recommendation.
Level of evidence based on the study design:
Thus, when searching for evidence-based information, one should select the highest level of evidence possible.
Systematic reviews, meta-analyses, and critically appraised topics/articles have all gone through an evaluation process: they have been "filtered."
Information that has not been critically appraised is considered "unfiltered."
As you move up the pyramid, however, fewer studies are available; it is important to recognize that high levels of evidence may not exist for your clinical question. If this is the case, you will need to move down the pyramid if your quest for resources at the top of the pyramid is unsuccessful.
Different types of clinical questions are best answered by different types of research studies. You might not always find the highest level of evidence (i.e., systematic review or meta-analysis) to answer your question. When this happens, work your way down to the next highest level of evidence.
This table suggests study designs best suited to answer each type of clinical question.
By: Amjad Alharthi