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Study Skills

Systematic Reviews: Search Strategy

Training and Support

Training and support are available in the following ways:

  • Top tips guides and video tutorials on how to use all the major databases
  • Introduction to literature searching training for University of Cambridge researchers/students, or for NHS staff. For those wanting more advanced searching training our database Q&A sessions are recommended.
  • You are also welcome to contact the training team at to arrange a one-to-one meeting. We would expect you to have attempted a literature search in advance, and have a clear idea of your research topic and the specific problems you are having, prior to arranging a one-to-one meeting.



Using PubMed in systematic reviews

While most of the standard medical, healthcare and interdisciplinary databases are appropriate for use in systematic reviews, Pubmed should be avoided. Pubmed lacks certain search functionality (for example the ability to code for proximity operators), making it different to search consistently across multiple databases. However, the biggest problem is that Pubmed searches are not reproducible and transparent. Pubmed:

'uses machine learning algorithms working behind the scenes which are invisible to the searcher. That means that transparency and reproducibility is no longer possible. Transparency and reproducibility are of key importance in scientific reporting and experiments. Without these present in the search strategy, a systematic review falls at the first hurdle when being critically appraised.

PRISMA-S was launched recently, outlining all the reporting requirements for literature searching in systematic reviews. Item 8 is: Include the search strategies for each database and information source, copied and pasted exactly as run. Note ‘exactly as run’. This is not possible in PubMed. Medline on the OVID platform (or via EBSCO or other aggregator) is preferred.'

Exploring the Evidence Base.

Search Strategy

The requirements for systematic reviews will mean that your literature search will need to be more complex and thorough than previous literature searching you may have done. You will need to come up with many synonyms for your search terms, and make sure that you are searching in the title, abstract and MeSH term fields of every database you use. Make sure you are using the Boolean operators AND, OR and NOT correctly, and make use of other search syntax such as truncation and wildcards to ensure your search is as comprehensive and efficient as possible.

Most systematic review search strategies use PICO to frame their search.


P: problem, patient/population, I: intervention(s), C: comparator(s), control, O: outcome(s)

Understanding search strategies

Systematic review search strategies are more complex than those you are perhaps used to — they frequently require tens or even hundreds of lines of search terms, a mixture of MeSH and freetext terms, translating search syntax from one database to another, and use of advanced search syntax such as truncation (using * to truncat* words), proximity (using code to search for words being within a certain number of words adjacent to each other), and wildcards (using ? to replace one letter with another).

This guide by the University of Exeter Library gives a detailed explanation of how to 'decode' search strategies in systematic reviews.

Where to Search

Find the material you need at:

  • Databases for literature searching: the Medical Library's curated list of the major medical, healthcare and scientific databases
  • Databases A-Z: the full list of databases available to University of Cambridge students and researchers. A Raven login is needed to access these remotely
  • NHS Athens resources: the full list of databases available to NHS staff. An Athens login is required to access these

Contact us

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Medical Library Team
University of Cambridge Medical Library
Box 111
School of Clinical Medicine
Cambridge Biomedical Campus
01223 336750

Useful tools for building your search

These tools will help you improve the quality of your search strategy:

  • Pubmed ReMiner: a tool to help you build your search by showing you the most commonly used freetext and MeSH terms used in articles about your topic
  • Visualizing Pubmed: provides various formats of data visualisation of the results you find in Pubmed
  • InterTASC Search Filters Resource: a collaborative venture to identify, assess and test search filters designed to retrieve research by study design or focus
  • SIGN methodology filters: pre-tested search filters designed to narrow results to particular study design types in a range of databases
  • Database Syntax: librarian Janneke Staaks has designed a resource which translates search syntax across the most commonly used database platforms
  • OECD countries search filter: search terms validated by NICE to limit your search to specific geographic regions



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