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Systematic Reviews and other Evidence Syntheses

Where to Search

The goal of the systematic literature search is to create a comprehensive search strategy using multiple databases, grey literature, and unpublished studies to find all of the relevant literature. The advanced search features of databases allow you to combine subject terms (i.e. MeSH) as well as keywords to construct a precise, reproducible strategy. Search strategies should be sensitive (exhaustive), rather than highly specific (narrow).

  • Cochrane considers Cochrane Library, MEDLINE, and Embase to be the minimum number of databases to search for a systematic review of trials.
  • Another general suggestion for medical systematic reviews is to search MEDLINE, Embase, a subject-specific database, Web of Science or Scopus, and Google Scholar. For more information about optimal combinations of databases, see the below article (Bramer, et. al., 2017).

Tools & Tips for Developing Searches

Developing a reproducible and replicable search is the most fundamental aspect of any evidence synthesis. Many published systematic reviews are reproducible and replicable. In order to make your systematic review or evidence synthesis the highest quality, we recommend attending a library webinar and reaching out to one our trained librarians.


Learn How to Develop a Search for a Systematic Review


Tools for Developing & Translating Searches

Grey Literature and Trials Databases

Grey literature is information produced outside of traditional publishing and distribution channels. Traditionally, systematic reviews include grey literature. This is especially important for systematic reviews including prospective research. It can include:

Type of grey literature Some examples of where to search to find
Clinical trials

WHO International Clinical Trials Registry Platform 

Reports, working papers, white papers, newsletters

Google (video on how search Google using advanced search)

Google Scholar

Browse relevant websites

Government documents

Google search (video on how search Google using advanced search)

Browse relevant websites

Conference proceedings, papers, posters, presentations

Website of the particular conference you're interested in



Theses & dissertations

ProQuest Dissertations & Theses Global

Google Scholar

Policy literature


Google (video on how search Google using advanced search)

Browse relevant websites



PubMed has a filter for preprints under the article types filters.

Mitigating bias in your search

Reproducibility of Search

A systematic review uses a structured and reproducible method to identify, assess and critically appraise all relevant studies in response to a specific research query.  Here are some tips for making sure your search is reproducible:

  • Use subject headings and field codes in your search strategies
  • Be aware that search algorithm in databases and search engines can negatively impact the reproducibility of your search
  • If using a search hedge (or filter) make sure that it is validated and cite the use of it in your methods
  • Run your searches on the same date and run updates on the same date as well
  • Use the PRISMA-S searching extension checklist to verify that every component of your search is fully documented and therefore reproducible


The search strategies documentation template can be used to help in your reporting of your search methods