The goal of a systematic review evidence search is to identify all studies that contain data pertinent to the research question. A comprehensive, transparent, and reproducible search of the literature is key to the validity of a systematic review's conclusions.
Most searches begin with a core database. Even though databases can have overlap in their content, you should run your search in multiple databases to be as comprehensive as possible. Think about each of the components of your question and be open-minded about which databases might have what you are looking for. Searching a subject-specific database may yield results not found in more general databases.
Your database searches must be comprehensive and systematic. In order to retrieve the greatest number of relevant results, you need will need to conduct a broad, sensitive search, as opposed to a narrow, specific search. You will need to search all of the terms, synonyms, previous terms, subject headings, and ways of conceptualizing each of your question's components that you can. A broad search may return more results that do not meet your inclusion criteria, however it is important not to miss any eligible studies.
How to Generate Search Terms
|Use your PICO components.||
In regards to each PICO concept, consider:
|Scope out key articles on your concepts.||
|Search databases' lists of subject headings.||
Note: the indexing process takes time and is not always immediately done for new articles, so do not rely solely on these terms.
|Use the Yale MeSH Analyzer to discover more MeSH terms.||
How to Modify Your Search With Boolean Operators:
Other search modifiers vary by database. Look for each database's Help or Tutorial pages to find more information. Here are some common modifiers:
Be sure to document all aspects of your search, including the terms, Boolean operators, search fields, and punctuation you used in each database, and the date each search was conducted. The goal is to make the search fully reproducible.
Your searches could potentially return a very large number of results, and you will want to keep a record of every single one of those, even the ones you end up excluding from your review! Using a citation management tool makes it easier to track and organize your search results throughout the review process. Importing results into one of these tools can help you to remove duplicates, screen for your criteria, access the publications, organize the results into folders, and format your citations, among other functions.
For more information about signing up for Covidence or linking your previous OSU or OSUMC affiliated Covidence accounts, please refer to our detailed graphic handout.
Citation Management Tools:
Tools designed specifically to help manage the systematic review process. Some have data extraction as well as citation management functions:
An exhaustive search for a systematic review must look beyond traditionally published literature to find all relevant research and minimize publication bias. Materials produced outside of the traditional commercial/academic publishing and distribution channels by organizations such as governments, businesses, NPOs, professional associations, and health organizations are known as grey literature.
Examples of grey literature:
Even a well-developed database search strategy can leave gaps, thanks to limitations in each databases' scope and indexing. These additional methods can help you discover studies that your search may have missed. Be sure to document the methods your team uses and your results:
|Reference Lists||Scanning the reference lists of your results can help find relevant studies missed by your search.|
|Alerts for New Publications||After creating profiles in databases, you can save your searches and set alerts for them so that you will be notified if anything new gets published. This is especially important if the topic of your review is a big focus in current research.|
Identify key articles you are including and search for other articles that have cited them.
|Handsearching||Identify key journals in your field that may or may not be included in the databases you chose and then manually scan their print or electronic contents for additional publications.|
|Contacting Experts||Experts can be helpful in ensuring that you have found all of the relevant research. They can also be sources of information on unpublished or ongoing research.|