Characteristics of a comprehensive search
A comprehensive search:
- uses multiple synonyms for each main concept
- uses advanced syntax
- is performed across multiple databases.
Prepare your comprehensive search
- Determine the searchable concepts in your research question. These may or may not correspond to your chosen mnemonic.
- Explore synonyms for each concept. Conduct a quick scoping search to find alternative search terms in the title and abstract of relevant results.
- Identify subject headings (standardised terms) for each concept. These vary between databases.
- Use advanced search syntax. Each database uses distinctive commands that determine how terms are searched, which fields are searched, and how concepts are combined.
- Create a concept table or download this template to keep track of your work.
Choose a database or platform
Each database or platform provides access to different collections of resources. Depending on your review question, consider searching both multidisciplinary and subject-specific databases.
- Multidisciplinary databases contain a high volume of literature from a diverse range of subjects. They are helpful in locating literature on your topic from disciplines you might not have considered. Scopus and Web of Science are multidisciplinary databases.
- Subject-specific databases contain in-depth coverage of literature that is highly specific to a particular field. Medline, PsycInfo, and CINAHL are subject-specific databases.
Platforms and databases suitable for comprehensive searches
Database platforms
Library databases are hosted on database platforms such as Ovid, EBSCO, and ProQuest. These platforms can hosts several different databases . For example, the Ovid platform hosts the Medline, Embase, and PsycInfo databases. These databases each use different subject headings and must be searched separately. You cannot run the same search in multiple databases on the same platform. When writing your protocol, make sure you mention the platform on which you will search the database (e.g. Medline via Ovid, CINAHL via EBSCO).
Medline
The Medline database is available through several platforms, including subscription (Ovid, Web of Knowledge, and EBSCO) and free (PubMed) options. We recommend searching Medline via Ovid for comprehensive and systematic searches, and PubMed for scoping searches. Constructing your search on Medline via Ovid provides increased control over search structure, aiding consistency in your methodology. If a researcher doesn’t have access to Medline, they can search PubMed instead. PubMed may be particularly useful for animal model-based research questions and studies in genetics.
Platforms and databases suitable for scoping searches and grey literature
Google Scholar
As Google Scholar searches are not reproducible, they are not suitable for systematic review searches. However, Google Scholar can be used for scoping searches due to its size and algorithm.
Google
As Google scans the entire web, a Google search can be used to find grey literature.
Grey literature is research that hasn’t been published commercially but is available outside of traditional academic sources (like books and journals). Using grey literature in a systematic review can reduce publication bias. Data not published commercially may impact your findings by altering the results.
Before starting a search
Before you start searching in a database, check the following:
- Does the database have a thesaurus? Look for a “map to subject headings/suggest subject terms” function on the database search page.
- What syntax does this database use? Look for search tips in the database Help section.
- Does the database have a “save search” function?
Search filters
Add filters to your database searches to find relevant research. Filters can limit results to a particular study type or topic or enhance your search by identifying additional terms.
Use “study type” filters when conducting a review of one study design only. Do not use this type of filter for reviews that allow multiple study designs in their eligibility criteria.
Study type filters
Other filters