How-to · Step-by-step
Literature search strategy
A literature search strategy is a planned, documented method for finding the relevant studies on a topic — built by breaking a question into concepts and translating each into searchable terms.
The step most authors miss
Doing CRediT right? Don’t stop at the statement.
A CRediT statement credits you inside one paper. The recognition CRediT was built for happens when those roles are tied to you, persistently. Sign in with your ORCID — free — and claim your CRediT contributions on casrai.org, the home of the standard. They become a verified, portable part of your identity, not a line that disappears into one PDF.
Free: claim your contributions, then export a journal-ready CRediT statement, schema.org structured data, JATS XML, CSV or BibTeX — and preview your public profile. A membership publishes that profile publicly and verifies the journals you serve.
Step by step
How to do it
1.Break the question into concepts
Decompose your research question into its key concepts. A structured frame such as PICO (Population, Intervention, Comparison, Outcome) or PICo for qualitative questions helps identify the two to four core concepts your search must cover.
2.List keywords and synonyms
For each concept, brainstorm every way authors might refer to it — synonyms, alternative spellings, abbreviations and related terms. Scanning a few known relevant papers for the words they use is a quick way to expand the list.
3.Add database subject headings
Many databases index records with a controlled vocabulary, such as MeSH in MEDLINE. Adding the relevant subject headings to your free-text keywords catches records that use different wording for the same concept.
4.Combine terms with Boolean operators
Join synonyms within a concept using OR to broaden, then join the different concepts using AND to focus the search on records that contain all of them. Use NOT sparingly, as it can exclude relevant records.
5.Refine with truncation and phrase searching
Use a truncation symbol (often *) to capture word variants — nurs* finds nurse, nurses, nursing — and quotation marks to search an exact phrase. Adjust these to balance sensitivity (finding everything) against precision (limiting noise).
6.Select and search several databases
Run the strategy across the databases relevant to your field, adapting the syntax to each, since no single database covers all the literature. Consider grey literature and reference-list checking to catch studies that databases miss.
7.Document and refine the strategy
Record every database, the exact terms, the operators, any limits and the dates searched, along with the number of results. Review the early results, refine the terms, and keep the final strategy so the search is transparent and reproducible.
Why a documented strategy matters
A search strategy is the engine of a literature review: the quality of what you can synthesise is capped by the quality of what your search retrieves. A planned, written strategy makes the search comprehensive enough to find the relevant evidence and transparent enough to be reproduced or updated — a requirement for systematic reviews, where the full search is reported alongside the results, but good practice for any review. Building it deliberately, rather than typing a phrase into one database, is what separates a defensible search from a haphazard one.
Common questions
FAQ
What is the difference between keywords and subject headings?+
Keywords are free-text words you choose, searched as they appear in titles, abstracts and text — flexible but dependent on authors using your exact wording. Subject headings are terms from a database’s controlled vocabulary, such as MeSH, applied by indexers to describe a record’s topic regardless of the words the authors used. Combining both makes a search more comprehensive than either alone.
How many databases should I search?+
No single database covers all the literature, so search several relevant to your field rather than relying on one. A systematic review typically searches multiple bibliographic databases plus sources of grey literature and reference lists. For a narrower review, the key databases for your discipline may suffice, but document which you used and why.
What is the trade-off between sensitivity and precision?+
Sensitivity (recall) is the share of all relevant studies your search finds; precision is the share of retrieved records that are actually relevant. Broadening with more synonyms, truncation and OR raises sensitivity but lowers precision, returning more to screen. Systematic reviews favour high sensitivity to avoid missing studies; a quick scoping search may accept lower sensitivity for manageable numbers.
Going deeper
