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Systematic Reviews

Recommended Library Databases

  • PubMed: A free database maintained by the U.S. National Library of Medicine, PubMed provides access to a vast collection of biomedical and life sciences literature. It is a foundational resource for systematic reviews in health, medicine, and related fields due to its extensive indexing of peer-reviewed journals.
     
  • Embase: A biomedical and pharmacological database known for its comprehensive coverage of European and international literature. Embase is especially valuable for systematic reviews as it includes many journals not found in PubMed and offers detailed indexing via Emtree terms.
     
  • Cochrane Library: A collection of high-quality databases focused on evidence-based health care, including the Cochrane Database of Systematic Reviews. It is essential for identifying existing reviews and controlled trials relevant to clinical decision-making.
     
  • PsycINFO: Managed by the American Psychological Association, PsycINFO covers literature in psychology, behavioral sciences, and mental health. It's particularly useful for systematic reviews involving psychological interventions, behavior, or mental health topics.
     
  • CINAHL: This database indexes nursing and allied health journals and is indispensable for systematic reviews in nursing, physical therapy, occupational therapy, and related healthcare fields.
     
  • Web of Science: A multidisciplinary citation database that provides access to high-impact journals and conference proceedings. It's valuable for systematic reviews due to its strong citation analysis and coverage across scientific and social science disciplines.

Grey Literature

Grey literature is research that is either unpublished or that hasn't been commercially published, such as by a book or journal publisher. 

Examples:

  • Theses and dissertations
  • Conference abstacts and procedings
  • Government reports
  • Article pre-prints and post-prints
  • Newsletters and bulletins
  • Research reports
  • Data sets

Why use grey literature in systematic reviews?

Paez (2017) offers compelling reasons: 

  • Including gray literature may increase the comprehensiveness of the search
  • Including evidence from a wide range of sources in a systematic review may enrich the review's findings and reduce the possibility of publication bias
  • Gray literature provides context for the question being examined, especially when a lack of consensus about the research question, or the setting or context of the intervention may affect its outcome, or there is a lack of available evidence in commercial publications
  • As there is sometimes a long lag time between the submission and publication of evidence, gray literature may help ensure the most current picture of what is happening within an area of practice at the time of the review

Citation: Paez A. Gray literature: An important resource in systematic reviews. J Evid Based Med. 2017;10(3):233-240. doi:10.1111/jebm.12266

 

Sources of Grey Literature

Online trial registries may include results of completed but unpublished clinical trials. These resources can be helpful in identifying otherwise unreachable trials and provide additional details of published trials. Many individual drug companies also have posted trial registries on their websites, although their quality varies. Even without results, knowledge that the trial exists can be helpful for reviewers, because they can contact the principal investigator for more information.