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Systematic Reviews: Medical Literature Databases to search

By Paul Levett

How to document your literature search

You should always document how you have searched each database, what keywords or index terms were used, the date on which the search was performed, how many results you retrieved, and if you use RefWorks to deduplicate results record how many were removed as duplicates and the final number of discrete studies you subjected to your first sift through of study selection.  Here is an example of how to document a literature search on an Excel spreadsheet, this example records a search of the hematology literature for articles about sickle cell disease. Here is another example of how to document a literature search, this time on one page of a Word document, this example records a search of the medical literature for a poster on Emergency Department throughput.  The numbers recorded can then be used to populate the PRISMA flow diagram summarizing the literature search.

In the final report add as an appendix the full electronic search strategy for each database searched for the literature review e.g. MEDLINE with MeSH terms, keywords & limits

In the final report in the methods section:

PRISMA checklist Item 7 information sources will be reported as:

  • What databases/websites you searched, the name of the database search platform and the start/end dates the index covers if relevant e.g. OVID MEDLINE (1950-present, or just PubMed
  • Who developed & conducted the searches
  • Date each database/website was last searched
  • Supplementary sources - what other websites did you search? What journal titles were hand searched, whether reference lists were checked, what trial registries or regulatory agency websites were searched, were manufacturers or other authors contacted to obtain unpublished or missing information on study methods or results.

PRISMA checklist Item 8 search will be reported as:

  • In text: describe the principal keywords used to search databases, websites & trials registers


What databases/indexes should you search?

At a minimum you need to search MEDLINEEMBASE, and the Cochrane CENTRAL trials register.  This is the recommendation of three medical and public health research organizations: the U.S. Agency for Healthcare Research and Quality (AHRQ), the U.K. Centre for Reviews and Dissemination (CRD), and the International Cochrane Collaboration (Source: Institute of Medicine (2011) Finding What Works in Healthcare: Standards for Systematic Reviews Table E-1, page 267).  Some databases have an alternate version, linked in parentheses below, that search the same records sets, ie the content of MEDLINE is in PubMed and Scopus, while the content of EMBASE is in Scopus. You should reformat your search for each database as appropriate, contact your librarian if you want help on how to search each database.  

Begin by searching:

1.       MEDLINE (or PubMed)


2.       EMBASE (or Scopus)  Please note Himmelfarb Library does not have a subscription to EMBASE. The content is in the Scopus database that you can search using keywords, but it is not possible to perform an EMTREE theasaurus search in Scopus.


3.       Cochrane Central Trials Register (or Cochrane Library). In addition Cochrane researchers recommend you search the and ICTRP clinical trial registries due to the low sensitivity of the Cochrane CENTRAL index because according to Hunter et al (2022) "register records as they appear in CENTRAL are less comprehensive than the original register entry, and thus are at a greater risk than other systems of being missed in a search."

The Polyglot Search Translator is a very useful tool for translating search strings from PubMed or Medline via Ovid across multiple databases, developed by the Institute for Evidence-Based Healthcare at Bond University. But please note Polyglot does not automatically map subject terms across databases (e.g. MeSH terms to Emtree terms) so you will need to manually edit the search syntax in a text editor to change to the actual subject terms used by another database.

The Yale Mesh Analyzer is another very useful tool you can copy and paste in a list of up to 20 PMID numbers for records in the PubMed database, the Yale Mesh Analyzer will then display the Mesh Medical Subject Headings for those 20 articles as a table so you can identify and compare what Mesh headings they have in common, this can suggest additional search terms for your PubMed search.

The MedSyntax tool is another useful tool, for parsing out very long searches with many levels of brackets. This would be useful if you are trying to edit a pre-existing search strategy with many levels of parentheses.

Some sources for pre-existing database search filters or "hedges" include:


Supplementary resources to search

Other member of your investigative team may have ideas about databases, websites, and journals they think you should search. Searching these sources is not required to perform a systematic review. You may need to reformat your search keywords.

Researchers at GW should check our subject research guides for suggestions, or check the libguides community for a guide on your subject.

In addition you may wish to search one or more of the following resources:

  • Google Scholar
  • BASE academic search engine is useful for searching in University Institutional Repositories
  • Cochrane Database of Systematic Reviews to search for a pre-existing systematic review on your topic
  • Epistemonikos database, has a matrix of evidence table so you can see what citations are shared in common across existing systematic reviews of the same topic. This feature might help identify sentinel or 'don't miss' articles.

You might also consider searching one or more of the following websites depending on your topic:

Clinical trial registers. The Cochrane Collaboration recommends for a systematic review to search both and the WHO ICTRP (See section 4.3):



Grey literature resources:



  • See our Himmelfarb preprints guide page on finding preprints, a useful database for searching Health Sciences preprints is Europe PMC


Dissertations and Theses:


Conference proceedings:

Most conference proceedings are difficult to find because they may or may not be published. Only select individual papers may be made available in print as a book, journal, or series, rather than all of the presented items. Societies and Associations may only publish abstracts, or extended abstracts, from a conference, often in an annual supplement to an issue of the journal of record of that professional society.  Often posters are not published, if they are they may be made available only to other conference registrants at that meeting or online. Authors may "publish" their conference papers or posters on personal or institutional websites.  A limited set of conference proceedings databases include the following:

  • BASE academic search engine, has an Advanced Search feature with a Limit by Type to 'Conference Objects', this is useful for searching for conference posters and submissions stored in University Institutional Repositories.
  • Web of Science - click All Databases and select Core Collection - under More Settings limit to the Conference Proceedings Citation Index (CPCI) - searches a limited set of conferences on Science, Social Science and Humanities from 1990-present.
  • Scopus - Limit Document Type to Conference Paper or Conference Review.
  • Proquest - Limit search results to conference papers &/or proceedings under Advanced Search.
  • BioMed Central Proceedings - searches a limited set of biomedical conference proceedings, including bioinformatics, genetics, medical students, and data visualization.
  • F1000 Research - browse by subject and click the tabs for articles, posters, and slides - which searches a limited number of biology and medical society meetings/conferences. This is a voluntary self-archive repository.


Individual Journals 

  • You may choose to "hand search" select journals where the research team reads the Table of Contents of each issue for a chosen period of time.  You can look for the names of high impact journal titles in a particular field indexed in Journal Citation Reports (JCR). Please note as of August 2021 ISI are linking to a new version of JCR that currently does not have the particularly helpful 'Browse by Category' link working, so I recommend you click the Products link in the top right corner and select Journal Citation Reports (Classic) to switch back to the old version to get that functionality back.



  • The AllTrials petition aims to motivate health care researchers to petition regulators and research bodies to require the results and data of all clinical trials be published.