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Gerstein Science Information Centre

Systematic & Scoping Reviews : Methodology Behind the Search Strategies

This guide is primarily for students and other researchers conducting systematic reviews and scoping reviews for coursework, thesis/dissertation requirements, or for other research purposes.

How Systematic/Scoping Review Strategies Differ from Typical Literature Reviews

There are several ways in how the search for information/articles/studies differs between a knowledge synthesis methodology and a regular/usual/typical review of the literature.

Aspect More detail

Knowledge syntheses are designed to minimize bias and be an objective methodology. Bias can include publication bias, negative results bias, selection bias, etc.

Bias is minimized by:

  • Not applying English-only limits
  • Not limiting by publication year unless a reason exists 
  • Searching a minimum of three journal article databases
  • Including grey literature (e.g. literature other than journals articles and books such as clinical trials, conference proceedings, reports, contacting experts/.authors for unpublished data, etc.)
  • Having more than one person screen for articles/studies to include (matching inclusion/exclusion criteria as defined in protocol)


A protocol is a plan for how your review will be conducted.  It sets out in advance:

  • The purpose or rationale behind conducting your study
  • The methodologies to be used (e.g. in finding reviews, in assessing the quality of reviews found, statistical methods, etc.)
  • Anticipated bias and how it will be addressed 
  • Determine in advance what outcomes you will be measuring
  • How will the data be synthesized



The search strategies should be transparent and reproducible.  It should not be a mystery as to how the articles/studies were found. The search stratgey section in the Methods section of the resulting published article should have enough detail so another can reproduce=uce the searches.  Details such as:

  • Names of databases (including platform - e.g. Ovid Medline, EBSCO CINAHL, etc.)
  • Year ranges
  • Date search was executed
  • Entire search strategy for each database (often included in the Appendices)
Grey literature

Grey Literature is any literature that has not been published through traditional means. It is often excluded from large databases and other mainstream sources.

Search grey literature to:

  • avoid bias
  • ensure that the review is as thorough as possible
  • find sources for negative results or brand new evidence
  • discover more references to published literature that your database search might have missed

More info on grey literature


Search filters, also known as hedges, are:

  • pre-cooked search strings that are designed to limit search results
  • designed to be highly-sensitive, precise, or a balance of both

Commonly, search filters limit search results by:

  • age group
  • publication type
  • study design

More info on filters, where to find them and how to use them

Expiration date Search strategies expire after 9 months.  Search strategies are required to be updated.


Steps in the methodology for searching for studies

Please note the steps below are the steps for conducting and documenting the search of the literature. This is just one part of the overall methodology for the knowledge synthesis study. There are more steps both before and after in conducting a systematic or scoping review.

chevron Formulate your research question
chevron Determine what (if any) reviews on your topic may already have been published
chevron Write your search protocol
chevron Conduct comprehensive search for studies (designed to minimize bias)
chevron Report search methodology with transparency so it can be reproduced

All searches for knowledge syntheses should be comprehensive and highly sensitive. For instructions on conducting this style of search, please consult Searching the Literature: A Guide to Comprehensive Searching in the Health Sciences or book an appointment with a librarian.