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Systematic Reviews, Scoping Reviews, and other Knowledge Syntheses

What is a systematic search?

Knowledge syntheses involve systematically searching the literature. For example,

Systematic reviews of interventions require a thorough, objective and reproducible search of a range of sources to identify as many relevant studies as possible (within resource limits). This is a major factor in distinguishing systematic reviews from traditional narrative reviews (...)

Lefebvre C, Glanville J, Briscoe S, Littlewood A, Marshall C, Metzendorf M-I, Noel-Storr A, Rader T, Shokraneh F, Thomas J, Wieland LS. Chapter 4: Searching for and selecting studies. In: Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.1 (updated September 2020). Cochrane, 2020. Available from https://training.cochrane.org/handbook/current/chapter-04#section-4-2-2

Systematic searching is:

  • Thorough: It involves searching more than one database and using a combination of textwords plus subject headings (the latter when available) to identify relevant literature. It also involves using supplementary search methods in addition to database searching
  • Objective: Search terms include variations in terminology and the searcher should avoid biasing the results of the search through the selection of search terms
  • Reproducible: The searcher is careful to record all the details of the search, including the database and platform with dates of coverage (may differ based on institutional subscriptions), the search strategy as executed, and the date the searches were run

Basic searching

MEDLINE is often considered a primary database for biomedical searches. It is available through various platforms including PubMed but at McGill we recommend searching MEDLINE on the Ovid platform.

Need help searching MEDLINE on Ovid?

Start with this introduction to searching with subject headings and keywords.

More information on the importance of the research question and the basics of searching can be found in the guide called Health Sciences Research Basics.

Selecting databases to search

Need help choosing which databases to search for a health sciences review? 

Chapter four of the Cochrane Handbook states that it is mandatory to search CENTRAL, MEDLINE, and Embase for all Cochrane reviews (4.3.1.1). Other databases are also suggested in the technical supplement to chapter 4, particularly if you are performing region- or subject-specific searches covered in more specialized databases (e.g., CINAHL, PsycINFO, or regional databases).

Bramer et al. (2017) recommend searching the following based on their analyses: Embase, Ovid MEDLINE ALL, Web of Science Core Collection, and the first 200 records in Google Scholar. Keep in mind that Web of Science Core Collection may include different indices depending on the institutional subscription. 

Large, multidisciplinary citation databases are certainly worth considering, particularly if studies on your topic are likely to be found across many disciplines.

Core databases

This table lists some of the differences between the core databases used in health sciences.

Database (Platform) Subject coverage Publication types included Dates covered
MEDLINE (Ovid) / PubMed Primary biomedical database for health care research; we recommend searching MEDLINE on the Ovid platform (enhanced options for searching) or via PubMed (free platform) Journal articles, editorials 1946 to present
CINAHL (EBSCOhost) Extensive coverage of nursing and allied health, including nursing and rehabilitation journals not covered by MEDLINE Journal articles, editorials, trade magazines 1937 to present
CENTRAL (Cochrane Library) CENTRAL is a sub-database (identified as Trials) in the Cochrane Library and contains records of randomized and quasi-randomized studies. The majority of the records come from MEDLINE and Embase but records from CINAHL and KoreaMed are also included, along with trial records from ClinicalTrials.gov, ICTRP, and additional records from handsearching and those flagged in the Cochrane Review Groups' Specialized Registers. Journal articles, records from clinical trial registries Earliest available to present
Embase Classic + Embase (Ovid) European coverage in biomedicine, rehabilitation, pharmacology Journal articles, editorials, conferences 1947 to present
PsycINFO (Ovid) Excellent resource for research on psychological, social, behavioural, and mental health questions Journal articles, books, book chapters, & dissertations 1806 to present
Scopus Multidisciplinary citation database; "largest database" of peer-reviewed article records covering the arts, medicine, science, social sciences, and technology Journal articles, books, conference proceedings 1823 to present
Web of Science Core Collection Multidisciplinary citation database; McGill coverage includes the Science Citation Index Expanded 1900- (SCI-EXPANDED), Social Sciences Citation Index 1956- (SSCI), Arts & Humanities Citation Index 1975- (A&HCI), Conference Proceedings Citation Index-Science 1900- (CPCI-S), Conference Proceedings Citation Index-Social Science & Humanities 1900- (CPCI-SSH), and the Emerging Sources Citation Index 2015- (ESCI) Journal articles, conference proceedings 1900 to present

Additional databases

  • If your question spans multiple disciplines and you would like more information on databases outside of this list, we suggest consulting the subject guides (also known as LibGuides) produced by McGill librarians to get a sense of resources available at McGill.
  • Other high-quality knowledge syntheses published in the area of your research question can also be used for guidance. Cross-reference the methods sections of published syntheses performed in the field of your synthesis topic.
  • Consider consulting topic experts for further guidance.
  • Preliminary/exploratory searches in databases you are considering including can also give you a sense of how useful the database will be.
  • The Cochrane group also has a living list of resources you can consult.

Peer reviewing your search

It is recommended that you have your search strategy peer reviewed. For peer review criteria and critical appraisal of search strategies, consult:

Developing and running the database searches

We recommend developing the search strategy in a primary database before translating the search strategy to the other selected databases: This will make it easier to keep track of things. If you subsequently find terms in the other selected databases, you can then go back and add them to the search(es) that has (have) already been developed as well as integrate them into the remaining searches.

We also recommend running all the searches on the same day to make it easier to document the date in your manuscript. 

Once you have your searches developed and you are ready to run them, you can the export the records from each database to an EndNote library, which you will keep for your files.

References

Booth A, Briscoe S, Wright JM. The “realist search”: A systematic scoping review of current practice and reporting. Research Synthesis Methods. 2020;11(1):14-35. doi: 10.1002/jrsm.1386

Bramer WM, de Jonge GB, Rethlefsen ML, Mast F, Kleijnen J. A systematic approach to searching: An efficient and complete method to develop literature searches. J Med Libr Assoc. 2018;106(4):531-41. doi: 10.5195/jmla.2018.283 (Open access)

Bramer WM, Rethlefsen ML, Kleijnen J, Franco OH. Optimal database combinations for literature searches in systematic reviews: A prospective exploratory study. Syst Rev. 2017;6(1):245. doi: 10.1186/s13643-017-0644-y

Cooper C, Booth A, Varley-Campbell J, Britten N, Garside R. Defining the process to literature searching in systematic reviews: A literature review of guidance and supporting studies. BMC Med Res Methodol. 2018;18(1):85. doi: 10.1186/s12874-018-0545-3 (Open access)

Lefebvre C, Glanville J, Briscoe S, Littlewood A, Marshall C, Metzendorf M-I, et al. Technical supplement to chapter 4: Searching for and selecting studies.  Cochrane handbook for systematic reviews of interventions version 6.1: Cochrane; 2020.

Morris M, Boruff JT, Gore GC. Scoping reviews: Establishing the role of the librarian. J Med Libr Assoc. 2016;104(4):346-53. doi: 10.5195/jmla.2016.156 (Open access)

Contact us

Notice

Due to a large influx of requests, there may be an extended wait time for librarian support on knowledge syntheses.

 

Find a librarian in your subject area to help you with your knowledge synthesis project.

 

Or contact the librarians at the
Schulich Library of Physical Sciences, Life Sciences, and Engineering
schulich.library@mcgill.ca

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