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Systematic Reviews & Other Syntheses

MEDLINE: Did you know?

You can search MEDLINE using PubMed or the Ovid interface. PubMed is a free resource that you will always be able to access, whereas Ovid MEDLINE is a proprietary resource that has been purchased by Queen's University Library. The Ovid interface allows adjacency searching (searching for terms within so many words of one another), which PubMed does not, and may be more user-friendly for new searchers than PubMed. 

Cochrane: Did you know?

The library provides access to two different interfaces for searching Cochrane: Wiley or Ovid.


Deciding where to search for studies will largely depend on the review type and topic. How many resources you search may depend on time constraints. Locating studies for syntheses often includes searching for both published and unpublished ("grey") literature.

Studies for your syntheses may be found in the form of:

  • peer-reviewed journal articles
  • conference abstracts or proceedings
  • dissertations and theses
  • governmental or private sector research
  • ongoing or unpublished clinical trials

Library Databases

Queen's University Library provides access to broad coverage databases in the health sciences (such as MEDLINE and Embase) as well as smaller subject-specific databases (such as PsycINFO and CINAHL). Depending on your review topic, it may also be appropriate to search in databases from other disciplines such as the social sciences, law or education.

Database comparison






Cochrane Library

Web of






Varies by database




> 8,500






> 26 million

> 30 million

~4 million

> 4 million

>1 million

>100 million

Record Types:

Journal articles, some conference materials

Journal articles, conference proceedings

Journal and magazine articles, dissertations, books

Journal articles, book chapters, dissertations

High-quality journal articles (controlled trials, systematic reviews)

Journal articles, book chapters, conference proceedings

Subject Headings:




APA Thesaurus Terms



QUL Platforms:

Ovid and PubMed



Ovid and

Ovid and

Web of


No need to search both Ovid MEDLINE and PubMed


“Cumulative Index for Nursing & Allied Health Literature”


Suite of databases

Multi-disciplinary (incl. social sciences, education etc.)


Selected library databases

Below is a list of the most popular health sciences databases that Queen's has access to. It is not a comprehensive list of potentially relevant databases. To discover more databases that might be relevant for your topic, try the Browse Databases by Subject feature on the library website or speak with a librarian.



Hand-searching relevant journals page by page can be incredibly time-consuming but it may identify additional studies that have been missed by database search strategies or studies from journals that are not covered in electronic databases.

Research evidence:

  • A systematic review by Hopewell et al. (2007) on the efficacy of handsearching to identify reports of randomized trials found that "...a combination of handsearching and electronic searching is the most comprehensive approach in identifying reports of randomized trials" (p. 2). However, the authors noted "...where time and resources are limited, searching an electronic database using a complex search will identify the majority of trials published as full reports in English language journals, provided, of course, that the relevant journals have been indexed in the database" (p. 2).

Conference proceedings

Databases may not index conference proceedings, and even if they do, coverage may be limited. Hand-searching relevant conference proceedings that are available on association or conference websites may identify additional relevant studies.

Searching Reference Lists

Once you have identified eligible studies for your knowledge synthesis by searching the appropriate resources above, it is best practice to then check the reference lists of these studies to identify any additional studies. The reference lists of related reviews may also help to identify additional studies.

Research evidence:

  • A systematic review was conducted by Horsley et al. (2011) to determine whether searching reference lists actually identifies additional studies during the systematic review process. Most studies included in their systematic review reported that this practice did identify additional studies; however, the evidence supporting this practice most often came from case report data and not high quality research. Despite this, Horsley et al. still recommend that systematic reviewers screen the reference lists of relevant studies to find additional studies, especially when you're struggling to find relevant information.

Cited Reference Searching

Citation indexes such as Web of Science (or the search engine Google Scholar) can be used for cited reference searching. Citation reference searching allows you to identify where eligible studies have later been cited to see if this identifies any additional studies.

For example, if you search for a relevant study in Google Scholar you will see a "Cited by..." link underneath the study information that indicates how many times the study has been cited (unless the study has not yet been cited). You can follow this link to view where the study has been cited to see if this locates any additional studies.


Cooper, C., Lovell, R., Husk, K., Booth, A., & Garside, R. (2017). Supplementary search methods were more effective and offered better value than bibliographic database searching: a case study from public health and environmental enhancement. Research Synthesis Methods, (October 2017), 195–223. 
Craven, J. and P. Levay (2019). Systematic Searching: Practical Ideas for Improving Results, Facet Publishing.

Hartling, L., Featherstone, R., Nuspl, M., Shave, K., Dryden, D. M., & Vandermeer, B. (2016). The contribution of databases to the results of systematic reviews: a cross-sectional study. BMC Medical Research Methodology, 16.
Hopewell, S., Clarke, M., Lefebvre, C., & Scherer, R. (2007). Handsearching versus electronic searching to identify reports of randomized trialsCochrane Database of Systematic Reviews2.

Horsley, T., Dingwall, O., & Sampson, M. (2011). Checking reference lists to find additional studies for systematic reviewsCochrane Database of Systematic Reviews, 10(8).

Lefebvre C., Glanville J., Briscoe S., Littlewood A., Marshall C., Metzendorf M.-I., Noel-Storr A., Rader T., Shokraneh F., Thomas J. & Wieland L.S. Chapter 4: Searching for and selecting studies. In: Higgins J.P.T., Thomas J., Chandler J., Cumpston M., Li T., Page M.J. & Welch V.A. (Eds). Cochrane Handbook for Systematic Reviews of Interventions version 6.0 (updated July 2019). Cochrane, 2019. Available from

Lefebvre, C., Glanville, J., Wieland, L. S., Coles, B., & Weightman, A. L. (2013). Methodological developments in searching for studies for systematic reviews: past, present and future? Syst Rev, 2(1), 78. 

McAuley, L., Pham, B., Tugwell, P., & Moher, D. (2000). Does the inclusion of grey literature influence estimates of intervention effectiveness reported in meta-analyses? The Lancet, 356(9237), 1228–1231. 

Papaioannou, D., Sutton, A., Carroll, C., Booth, A., & Wong, R. (2009). Literature searching for social science systematic reviews: consideration of a range of search techniques. Health Information & Libraries Journal, 27(2), 114–122.

Schmucker, C. M., Blümle, A., Schell, L. K., Schwarzer, G., Oeller, P., Cabrera, L., … Consortium,  on behalf of the O. (2017). Systematic review finds that study data not published in full text articles have unclear impact on meta-analyses results in medical research. PLOS ONE, 12(4).

Stansfield, C., Dickson, K., & Bangpan, M. (2016). Exploring issues in the conduct of website searching and other online sources for systematic reviews: how can we be systematic? Systematic Reviews, 5(1).