A meta-analysis will thoroughly examine a number of valid studies on a topic and combine the results using accepted statistical methodology as if they were from one large study. Some clinicians put meta-analysis at the top of the pyramid because part of the methodology includes critical appraisal of the selected RCTs for analysis.
Systematic reviews usually focus on a clinical topic and answer a specific question. An extensive literature search is conducted to identify all studies with sound methodology. The studies are reviewed, assessed, and the results are summarized according to the predetermined criteria of the review question.
Authors of critically-appraised topics evaluate and synthesize multiple research studies, so that practitioners may more readily determine if the evidence is valid and reliable, and whether they can apply it to their own practice.
Authors of critically-appraised individual articles evaluate and synopsize individual research studies so that practitioners may more readily determine if the evidence is valid and reliable, and whether they can apply it to their own practice.