Research Guides: Systematic Reviews (in the Health Sciences): Grey Literature

Grey Literature

The term grey literature refers to all information that isn't commercially published. This can include the following types of documents:

Conference proceedings, abstracts, papers, posters, presentations, etc.
Clinical trials
Theses and dissertations
Regulatory documentation
Government reports
Grant proposals and applications
Social media posts
Etc.

Including grey literature in a systematic review can strengthen the overall product by minimizing publication bias. All sources of information, including grey literature, which is rarely peer reviewed, should undergo quality assessment and appraisal before being included in the final SR analysis.

For a more detailed explanation, see ITEM 2A: ONLINE RESOURCES of the PRISMA-S Explanation and Elaboration document.

PRISMA-S (Searching)

Grey Literature Resources

Health Sciences Grey Literature Guide

ClinicalTrials.gov

ClinicalTrials.gov is the result of a government mandate requiring clinical trials to register with the US government regardless of their intent to publish results. Including ClinicalTrials.gov in your search strategy can potentially strengthen a systematic review by including data not found in the published literature thereby minimizing bias.

ClinicalTrials.gov This link opens in a new window
Registry and results database; includes information about publicly & privately funded studies including; completed & ongoing trials, research design, results, and contact information.

More Clinical Trial Registries

WHO International Clinical Trials Registry Platform This link opens in a new window Central database with access to clinical trial data sets from international trial registries around the world.
ISRCTN Registry This link opens in a new window The ISRCTN (International Standard Randomised Controlled Trial Number) registers all clinical research studies (proposed, ongoing or completed) and provides each one with a unique identifying number. All study records in the database are searchable and freely accessible.
Clinical Trials Registers This link opens in a new window International listing of clinical trials registers compiled by the York Health Economics Consortium, University of York, UK.
ClinicalTrials.gov This link opens in a new window Registry and results database; includes information about publicly & privately funded studies including; completed & ongoing trials, research design, results, and contact information.
European Clinical Trials Database This link opens in a new window Register to make clinical trial results publicly available through the European Union Clinical Trials Register.
European Union Clinical Trials Register This link opens in a new window Search for protocol and results information on interventional clinical trials conducted in the European Union (EU) and the European Economic Area (EEA); and those conducted outside the EU / EEA that are linked to European paediatric-medicine development.
Centerwatch Clinical Trials This link opens in a new window Search clinical trials or browse by medical condition, therapeutic area, or location.
The Yale University Open Data Access (YODA) Project This link opens in a new window A digital repository for clinical research data. The YODA project provides access to the clinical datasets by request. This is useful for gaining access to complete clinical datasets.