Clinical and Research Support (old)

As systematic reviews aim to be comprehensive in the evidence they review, multiple databases must be searched. For example the Cochrane Library recommends searching:

• Medline or PubMed (not both, they have the same content)
• Embase
• The Cochrane Central Register of Controlled Trials (CENTRAL)
• subject specific databases
• local (national or regional) databases

You may also want to include:

• articles citing key papers - use Google Scholar or CitationChaser to identify citations
  • Note. Scholar is easy to use but does not allow bulk import into reference managers, CitationChaser does.
• dissertation and theses databases (eg ProQuest Dissertation & Theses Database)
• grey literature databases
  • grey literature can be hard to find. See our grey literature guide and using Google for Research for some sources and tips. 
• key journal archives
• other trial registries (eg  WHO's International Clinical Trials Registry Platform, ClinicalTrials.gov)
  • Trial registries should be searched for unpublished trials to reduce influencing results by publication bias.
  • Searching clinical trials registers: guide for systematic reviewers. BMJ 2022

Searches should be saved for each database so that search strategies can be reproduced in the final report. Records should also be kept of when key searches were carried out.

See our Guide to literature searching for advice on searching.

In order to be as comprehensive as possible it is recommended that searches are as broad as possible with inclusion or exclusion decided at the screening stage. Tightly targeted searches risk failing to identify relevant papers.

Meta-evidence blog - Searching Grey Literature