Grey Matters: a practical tool for searching health-related grey literature

Now revised and updated, explore CADTH’s free online resource for grey literature searching, “Grey Matters: a practical tool for searching health-related grey literature.”

Grey Matters: a practical tool for searching health-related grey literature

In order to use the tool:

  • save file
  • open file
  • “Open as read only?” will appear
  • click “No”


CADTH — the Canadian Agency for Drugs and Technologies in Health — provides Canada’s federal, provincial, and territorial health care decision-makers with objective evidence to help make informed decisions about the optimal use of drugs and medical devices  in our health care system. To achieve its mandate, CADTH produces a variety of publications that range from comprehensive systematic reviews and economic evaluations to more concise bulletins and updates.

In order to search for and retrieve the evidence base required to produce CADTH reports, CADTH’s Research Information Services team has developed and made available a grey literature checklist. Grey literature includes government information and reports that are not published commercially and that may be inaccessible via bibliographic databases. This checklist is used to:

  • ensure the retrieval of all relevant health technology assessment (HTA), government, and evidence-based agency reports that may not be indexed in bibliographic databases such as MEDLINE
  • document the grey literature search process, thereby increasing transparency and the potential for reproducibility
  • ensure that grey literature searching is done in a comprehensive way, according to international standards.1-2


This checklist is intended for librarians; information specialists; and researchers who are producing systematic reviews, HTAs, drug assessments, or economic evaluations.


The CADTH grey literature checklist is not exhaustive, but it does strive to be comprehensive regarding Canadian and international HTA agencies. To compensate for the focused characteristics of the checklist, supplemental keyword searches on search engines such as Google are recommended.

The checklist is updated every two years to ensure the website links and search tips are accurate, and to incorporate new sources. However, because of the continuously evolving nature of the Internet, CADTH cannot be held responsible for occasional inaccuracies due to website changes.

How to use this checklist

Organized by topic, the checklist includes tips on navigating the websites. Although the websites are usually assigned to only one category, in many cases an individual website may have relevancy in additional categories. The checklist does not supply background information on the agencies. If available, however, the name of the website is hyperlinked to a brief description of the agency.

This checklist is meant to be used to document all aspects of the search process. This includes the documentation of keywords used in the search, and information about the availability of each website, as well as the use of a drop-down box beside each website to indicate the success or relevancy of the retrieval.

Selective or targeted searching by category may be required, and time spent will vary according to the needs of a particular project.  A recent study highlights the average time spent searching grey literature for systematic reviews as being roughly a quarter of overall searching time.3   It is not mandatory to search every website on this checklist in order to conduct a comprehensive grey literature search.

Other CADTH searching tools and resources

A concise shortlist of the Grey Matters checklist has also been produced, entitled Grey Matters Lite. Grey Matters Lite, and a variety of other literature searching tools and resources provided by CADTH Research Information Services are available at Finding the Evidence: Literature Searching Tools in Support of Systematic Reviews.


  1. Lefebvre C, Glanville J, Briscoe S, Littlewood A, Marshall C, Metzendorf MI, Noel-Storr A, Rader T, Shokraneh F, Thomas J, Wieland LS. Technical supplement to Chapter 4: Searching for and selecting studies. In: Higgins JPT, Thomas J, Chandler J, Cumpston MS, Li T, Page MJ, Welch VA (eds). Cochrane handbook for systematic reviews of interventions. Version 6. Cochrane; 2019.
  2. Higgins JPT, Lasserson T, Chandler J, Tovey D, Churchill R. Standards for the conduct of new Cochrane Intervention Reviews. In: Higgins JPT, Lasserson T, Chandler J, Tovey D, Churchill R. Methodological Expectations of Cochrane Intervention Reviews. Cochrane: London, 2016. See Searching for studies
  3. Saleh A, Ratajeski M, Bertolet M. Grey literature searching for health sciences systematic reviews: a prospective study of time spent and resources utilized. Evidence Based Library and Information Practice 2014;9(3):28-50.