Evidence Synthesis: Citation Searching

Systematic review searches are distinctive in their comprehensiveness. Studies show that consulting with a librarian improves the quality of systematic review searches. Librarians can advise on the most appropriate search strategies and databases.

Complex searches for evidence synthesis is a multistep process. 

1. Identify key concepts for search
2. Gather search terms including synonyms for each concept
3. Subject heading lookup for each search term
4. String the search together with Boolean operators
5. Test the search
6. Translate to other databases 

Searches usually include databases and grey literature in an effort to locate all relevant studies, both published and unpublished.

• Bibliographic Databases
• Grey Literature
• Handsearching
• Citation Searching

A minimum of three bibliographic databases should be searched for systematic reviews.

Librarians can recommend subject specific databases tailored to your research question.

Grey literature includes conference papers, dissertations, theses, trial registers, etc. It is not controlled by commercial publishing. 

A few repositories of grey literature are:

Handsearching involves searching selected journals and conference proceedings 'by hand' in order to locate additional references not included in bibliographic databases or search results due to poor indexing.

Once full-text screening is complete, use your landmark studies to search for additional references. Search for potentially relevant articles they cite as well as articles published later that cite your landmark studies.  This procedure is sometimes called citation chaining. 

Useful databases for citation chaining include:

For guidance on when and how to report citation chaining, refer to the TARCiS statement.

Once the search strategy is complete, you will:

1. Run the search in each database on the same day
2. Export the results as an RIS file
3. Import the records into your citation management tool or screening tool
4. Download citations and abstracts

PRISMA-S provides guidance on how to report your search. Document the following:

• database name, platform, coverage years
• date of initial search and any updates
• search details including search terms, Boolean operators, subject headings, etc. 
• number of results

1. Hirt J, Nordhausen T, Fuerst T, Ewald H, Appenzeller-Herzog C; TARCiS study group. Guidance on terminology, application, and reporting of citation searching: the TARCiS statement. BMJ. 2024;385:e078384. Published 2024 May 9. doi:10.1136/bmj-2023-078384