Systematic Reviews, Scoping Reviews, and Other Knowledge Syntheses

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

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 given its increased functionality. Health sciences librarians will often start by developing an exploratory or preliminary search in MEDLINE, but this choice will also depend on the review question.

Need help searching MEDLINE on Ovid and other databases/platforms? Start with this introduction to searching with subject headings and keywords, using truncation and wildcards, and structuring a search with operators (e.g., Boolean OR and AND) and parentheses. 

View these tutorials on getting started and on searching Ovid MEDLINE, PubMed, and CINAHL, or search the web for tutorials on how to maximize the effectiveness of your searches in other databases/platforms.

Advanced searching in the context of knowledge syntheses often involves collaboration with a librarian or information specialist.

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

For more advanced searching and screening tools, see AI and text mining for searching and screening the literature

Worksheet for search terms

Keep track of the terms you will be using in your search strategy in whatever way works best for you. Below, we provide an example of a worksheet that can be used for this purpose. Depending on your research question, the list of terms can get quite long and can be difficult to manage if you are not recording them as you are finding them.

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 (the latter when available to the review team, which is the case at McGill) 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 indexes depending on the institutional subscription. 
• See the table below for other frequently searched databases in health sciences, or consult a health sciences librarian.

The Cochrane group also has a living list of resources you can consult.

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

• Global Index Medicus

If your question spans multiple disciplines and you would like more information on databases outside of this list, we suggest

• Consulting the library guides (also known as LibGuides) produced by McGill librarians to get a sense of resources available at McGill.
• Referring to other high-quality knowledge syntheses published in the area of your research question. Cross-reference the methods sections of well-conducted syntheses published in the field of your synthesis topic.
• Consulting topic experts for further guidance
• Conducting preliminary/exploratory searches in databases you are considering including, to give you a sense of how useful the database will be.
• Try the Search Smart database: Allows you to compare over 90 databases and their search systems. Note that not all databases are available at McGill. To quickly check most of our database subscriptions, see Databases A-Z.

It is recommended that you have your search strategy peer reviewed. Not all librarians will agree to peer review a non-librarian search, however. For peer review criteria and critical appraisal of search strategies, consult:

• McGowan J, Sampson M, Salzwedel DM, Cogo E, Foerster V, Lefebvre C. PRESS Peer Review of Electronic Search Strategies: 2015 Guideline Statement. J Clin Epidemiol. 2016 Jul;75:40-6. doi: 10.1016/j.jclinepi.2016.01.021. Epub 2016 Mar 19. PubMed PMID: 27005575.

• PRESS Peer Review of Electronic Search Strategies: 2015 Guideline Explanation and Elaboration (PRESS E&E) (see Table 9 for the updated checklist)

• PRESS Guideline — Search Submission & Peer Review Assessment: Microsoft Word format (Appendix A in Guideline Statement)

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.

You can use a tool called SRA Polyglot (with caution) to help with the search translation from MEDLINE on Ovid or from PubMed to a number of databases, such as CENTRAL (Cochrane Library/Wiley), CINAHL (EBSCOhost), Embase (Ovid), Scopus, and Web of Science Core Collection. It does not translate the subject headings, however, and you will need to do that manually (identifying the applicable subject headings in CINAHL and Embase, for example, then updating the searches accordingly, and removing them from databases in which they may have become redundant or nonsensical, e.g., when words are inverted). We also caution that using it properly requires more advanced database searching skills: It may not translate search fields accurately, and may leave in extraneous data.

The University of South Australia has some handy PDF guides on search translation:

Run your search on other databases

• Instructions for translating a search to Scopus, Web of Science, CINAHL, SPORTDiscus (EBSCOhost), Cochrane Library, ERIC (ProQuest), and ProQuest Dissertations and Theses Global

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 then export the records as .ris files. These can be imported into citation software or into knowledge synthesis software such as Covidence.

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)

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

Online training resources