This page will guide you in planning, developing, appraising, documenting and updating your searches.
A search of the literature must be systematic to be transparent, replicable, consistent, accountable and authentic.
Developing a comprehensive and effective search strategy is key to a well-defined research question. This is an iterative process, which involves continued evaluation and refining.
This search of the evidence is sometimes a balance between precision and sensitivity.
Precision - concepts are clearly and easily define and the question can be answered with a high degree of certainty:
I only require a small number of recent articles on obesity and quality of life.
Sensitivity - concepts more complex to describe and require gathering many sources of evidence:
I am undertaking a review of the literature.
Supplementary methods for searching such as citation searching, hand searching, web searching, contacting study authors or experts and trial register searching are becoming more important. These methods can add value to identifying study types for reviews since as content may not be found by searching only in databases.
The guidance handbooks for methodologies give direction on how to use these methods but further research is needed to determine how these methods actually work and how effective they are.
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Citation searching Topic areas no consistent terminology. Searches focus on connections between studies. Scopus, Web of Science and Google Scholar. |
Forward citation searching
Papers cited after publication.
Looking forward in time.
Contribution to scholarly conversation. |
Backward citation searching
Author citing papers.
Looking back in time. How the starting paper evolved. |
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Hand searching
Journal(s) not indexed in a database.
Finding studies in supplementary / special editions.
Manual check through print/online journals. |
Web searching Published/unpublished studies / grey literature (not indexed or included in databases or missed in searches. |
Contacting study authors or experts
Obtain more detailed information.
Difficult for older papers. |
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Trial registers
Recently completed trials / unpublished trials.
Tracking changes to trial protocols / reported outcomes. |
Further reading:
Cooper, C., Booth, A., Britten, N. et al. (2017) ‘A comparison of results of empirical studies of supplementary search techniques and recommendations in review methodology handbooks: a methodological review’. Syst Rev 6, 234,https://doi.org/10.1186/s13643-017-0625-1.
Use different functionalities within databases such as index terms (MeSH, Subject Headings and Thesaurus).
These index terms are controlled vocabulary within databases and when used together with free text keywords (title, abstract, keyword) will help to focus searches to create comprehensive search strategies.
Databases enable searching in fields such as title, abstract, author...
Note: there may be a difference in description of an index term across databases.
Further reading:
Levay, Paul, Craven Jenny (2019) Systematic searching practical ideas for improving results, Ebook Central.
Search filters are created to search difficult concepts or concepts which require a number of search terms.
Save time and effort – Overall creation of the search strategy / Number of records to be screened
Specific types - Study types such as systematic review/randomised controlled trial / Topic area
*A number will have been approved for effectiveness, others checked but not approved for preciseness, clarity, precision and sensitivity.
*Search filters not available on all databases, some are particular to a database interface based on the controlled vocabulary and the syntax within that database.
* It is better to assess how a filter might impact on search results before your search is completed.
The ISSG Search Filter Resource
Documenting the search strategies in a clear and transparent way for replicability
Reporting & critiquing to ensure clarity, quality control, self-audit and reflective learning for the searching process.
AMSTAR 2: a critical appraisal tool for systematic reviews that include randomised or non-randomised studies of healthcare interventions, or both
CONSORT - Consolidated Standard of Reporting Trials The CONSORT-Outcomes 2022 Extension.
Equator network - promotes the transparency and accuracy of reporting health research and the broader use of robust guidelines for reporting.
PRISMA- Preferred Reporting Items for Systematic Reviews and Meta-Analyses. PRISMA-S – Reporting literature searches in systematic reviews.
PRESS - Peer Review of Electronic Search Strategies checklist.
Search summary tables (SST) to determine the effectiveness of search methods for databases and supplementary sources to inform future searching and methods for research in searching.
Further reading:
Bethel AC, Rogers M, Abbott R. (2021) ‘Use of a search summary table to improve systematic review search methods, results, and efficiency’. J Med Libr Assoc., 109(1):97-106.
Rader, T., Mann, M., Stansfield, C., Cooper, C. and Sampson, M. (2014), ‘Methods for documenting systematic review searches: a discussion of common issues’. Res. Syn. Meth., 5: 98-115. https://doi.org/10.1002/jrsm.1097