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Systematic Reviews (in the Health Sciences)

Guidance for conducting health sciences systematic reviews.

Grey Literature

The term grey literature refers to all information that isn't commercially published. This can include the following types of documents:

  • Conference proceedings, abstracts, papers, posters, presentations, etc.
  • Clinical trials
  • Theses and dissertations
  • Regulatory documentation
  • Government reports
  • Grant proposals and applications
  • Social media posts
  • Etc.

Including grey literature in a systematic review can strengthen the overall product by minimizing publication bias. All sources of information, including grey literature, which is rarely peer reviewed, should undergo quality assessment and appraisal before being included in the final SR analysis.

For a more detailed explanation, see ITEM 2A: ONLINE RESOURCES of the PRISMA-S Explanation and Elaboration document. 

Grey Literature Resources is the result of a government mandate requiring clinical trials to register with the US government regardless of their intent to publish results. Including in your search strategy can potentially strengthen a systematic review by including data not found in the published literature thereby minimizing bias.

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