Knowledge Synthesis: Systematic, Scoping & Other Reviews

All applicable sources need to be searched to locate studies and eliminate bias.  Consult with a subject librarian or find suggestions from UBC Library research guides to locate key resources.

There are two key types of sources to search - licensed databases and alternate sources. Techniques for finding alternate sources include searching sources for grey literature; backward and forward reference chaining; hand searching; and contacting experts in the field.

We recommend Ovid Medline, rather than PubMed, for systematic reviews for several reasons. Ovid Medline allows you to:

• easily read your search, because terms are on separate lines
• use adj operator for proximity searches
• discover relevant MeSH terms more easily (PubMed's mapping functionality is often more limited)

Some systematic reviews state in their methods section that they've searched both Medline and PubMed. However, there's nearly complete overlap between Ovid Medline and PubMed so there's generally not a need to search them independently.

Should you prefer to search PubMed for your systematic review, consider contacting your subject librarian for help devising your search strategy.

See also: 

MEDLINE, PubMed, and PMC (PubMed Central): How are they different?

Ovid's Medline Compared To PubMed

If you are searching "Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE® Daily and Ovid MEDLINE® 1946-Present" effectively, there is no reason to ALSO search PubMed. Ask your librarian for details.

Citation searching, also sometimes referred to as 'citation chasing' or citation chaining', describes the search process used to exploit citation relationships to find additional articles beyond your database searches.

It is recommend to carry out citation searching once articles retrieved from the database searches have been screened and compiled into a list of included articles only. Citation searching methods can then be applied to papers that will be included in your review.

• Forward citation searching: retrieving and screening citing references.
  • Examine what later studies have cited significant studies.
• Backward citation searching (also referred to as 'reference list checking'): retrieving and screening cited references.
  • Check out the citations in the reference lists of major studies. 

See the TARCiS Statement for more information and citation searching reporting checklists.

Handsearching means manually looking through journals and/or journal websites of interest to check that nothing was missed when searching licensed databases. For your topic, consider handsearching specific journals that are not already indexed in the databases you are searching (ask your librarian if you need help determining where a journal is indexed).

You can access journal websites via the UBC Journal Search function; accessing journal websites in this way will help ensure you have access to any full-text articles you find.

Another idea for uncovering unpublished research is to identify key researchers working on your topic of interest to identify studies in process. For instance, you might be able to get additional data on a study described in a clinical trials register or conference abstract, or on a review protocol.

Grey literature refers to materials that aren't published in a traditional way, including dissertations, conference proceedings, clinical trials, and clinical practice guidelines. These sources aren't usually covered in regular licensed databases. Below are some tools for finding grey literature.

Preprints are manuscripts which may have been submitted to a journal, but not yet published. They have not yet gone through a formal peer review process, but some preprint servers do allow other researchers to post comments.

Preprint Repository Table