A systematic review is a comprehensive survey of a topic. It includes all primary studies of the highest level of evidence that have been identified, evaluated and then summarized according to a specific criteria.

A meta-analysis is a survey that includes the results of statistically similar studies. These results are then combined and analyzed as if it was one study.

These studies rank high on the Hierarchy of Evidence, and if done properly, such studies are more useful to Practice than an individual study.