A systematic review is a comprehensive literature search and synthesis project that tries to answer a well-defined question using existing primary research as evidence. A protocol is used to plan the systematic review methods prior to the project, including what is and is not included in the search.
Systematic reviews are often used as the foundation for a meta analysis (a statistical process that combines the findings from individual studies) and to re-evaluate clinical guidelines.
Systematic review and meta analysis are both types of evidence synthesis methods. Read more about evidence synthesis on the Should You Do a Systematic Review and Types of Reviews pages of this guide.