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Systematic Reviews: Intro

An introduction to the requirements, search strategies and resources needed to conduct the literature review portion of a Systematic Review

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Author

Becky Morin
Contact:
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Guidelines for writing Systematic Reviews

What's required?

In order to be thorough and systematic, multiple databases must be used and grey literature must also be searched if it is applicable. The Cochrane Collaboration recommends searching a minimum of three databases:

  • The Cochrane Central Register of Controlled Trials
  • MEDLINE (via PubMed or OVID)
  • EMBASE (usually searched via Scopus)

The Cochrane Collaboration also specifies that:

  • Searches should seek high sensitivity, which may result in relatively low precision.
  • Too many different search concepts should be avoided, but a wide variety of search terms should be combined with OR within each concept.
  • Both free-text AND subject headings should be used.

Your inclusion/exclusion criteria are extremely important and allow you to make your results more precise after you've conducted a search to find as much as you can that touches on your topic of interest.

Just as in clinical or bench research, a detailed methodology of your search strategy, results and inclusion/exclusion criteria must be included in your review so that it is reproducible. PRISMA standards require you to fill out a flow diagram and provides a helpful checklist to determine if your SR is complete.

How long do they take?

Remember the evidence pyramid and how few systematic reviews and meta-anaylses there are? This can be attributed to a few factors:

  • Many topics do not have enough lower-level research completed to create a thorough SR
  • Many topics do not lend themselves to "pure" SRs
  • Requirements for SRs are stringent, causing many attempts to fall short in methodology
  • High-quality SRs take a lot of TIME and effort.

The Cochrane Collaboration estimates about a year to complete the process, and this is often by teams of people working together on one review.