A systematic review is fundamentally different from a traditional narrative review. For more information, see Types of Literature Reviews.

A systematic review is defined as: "A scientific investigation that focuses on a specific question and that uses explicit, planned scientific methods to identify, select, assess, and summarize the findings of similar but separate studies. It may or may not include a quantitative synthesis of the results from separate studies (meta-analysis) depending on the available data." IOM p 1.

According to the Cochrane Handbook, section 1.2.2, "the key characteristics of a systematic review are:

• a clearly stated set of objectives with pre-defined eligibility criteria for studies;
• an explicit, reproducible methodology;
• a systematic search that attempts to identify all studies that would meet the eligibility criteria;
• an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and
• a systematic presentation, and synthesis, of the characteristics and findings of the included studies."

Green S, Higgins JPT, Alderson P, Clarke M, Mulrow CD, Oxman AD. Chapter 1: Introduction. In: Higgins JPT, Green S (editors),  Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 (updated March 2011). The Cochrane Collaboration,  2011. Available from www.cochrane-handbook.org.

Did you know that there is a specific methodology for systematic reviews? A systematic review requires:

1. More than one screener
2. Extensive search strategies utilizing both controlled vocabulary terms and keywords
3. Searching multiple databases
4. Establishing inclusion/exclusion criteria prior to searching
   • For more information, read the Institute of Medicine's Standards for Systematic Reviews

You can also use this primer geared towards beginners for a better understanding of the differences between types of reviews and the overall steps of a systematic review:

• Craig A. Umscheid; A Primer on Performing Systematic Reviews and Meta-analyses, Clinical Infectious Diseases, Volume 57, Issue 5, 1 September 2013, Pages 725–734, https://doi.org/10.1093/cid/cit333

The goal of a systematic review is to reduce bias and produce high quality evidence.

Rigorous systematic reviews are at the top of representations of research evidence (see below). The synthesis of multiple high-quality studies creates a single product out of all the best known evidence.

(from the University of Pittsburgh)