Search filters, sometimes called ‘hedges’, are search strategies that have been devised and tested to filter the results of your search. They represent a quick and efficient way to search for certain information. Many databases feature built-in search filters and many have been designed by search experts from various institutions.
Search filters fall into two broad categories:
Click the the Database tab in this box to find out how to search with filters in the CINAHL, Medline, PsycINFO and PubMed databases.
PLEASE NOTE: Search filters are often pre-tested or appraised for their performance, and can involve experts and a rigorous methodology to ensure performance is maximised. However others have not been validated and should be used with caution. For more information on critical appraisal of search filters please see the InterTASC website.
Methodological filters cover both study designs and/or focus e.g. adverse effects or observational studies.
The following list provides links to search filter pages designed by experts at various institutions:
Scottish Intercollegiate Guidelines Network (SIGN) Search filters
Filters for finding measurement properties. Includes filters for PubMed, Medline (Ovid), Embase and CINAHL.
Search filters (Chapter 4, 4.4.7)
Topic or subject filters help you retrieve information in a particular discipline area. Examples include:
Some databases have developed filters that can be used in addition to a subject search.
PLEASE NOTE: These filters are not as robust as those that are included on the InterTASC website.
Databases on the Ovid platform (Medline, Embase, PsycINFO, Ovid Emcare and Joanna Briggs Institute EBP Database.)
Perform a search for your topic then select Additional Limits in the search box.
Select from the following filters which vary according to each Ovid database:
Further Ovid expert searches can be found on the Ovid Expert Searches page.
Perform a search on your topic and then select Show More on the left hand side of the results page.
The following filters are available:
Additional study designs can be found by using Suggest Subject Terms on the search page and typing in a term such as Clinical Trial and expanding the term.
When conducting a search strategy for a systematic review, it is important to conduct a comprehensive (sensitive) search so that no relevant articles are missed. However, there is always a tradeoff between comprehensiveness (sensitivity) and precision.
The aim of the search strategy is to maximise the retrieval of relevant documents and minimise the retrieval of non-relevant material thus striking a balance between:
sensitivity (recall) and precision.
A sensitive search:
To increase sensitivity in your search:
A precise search:
To increase precision in your search:
Why do text mining?
Method 1 - Use a set of highly relevant articles
Method 2 - Use text mining tools
PRESS stands for Peer Review of Electronic Search Strategies. It is believed that quality is enhanced when there is peer review of the electronic search strategies developed for systematic review (SR) and health technology assessment (HTA) reports.
The PRESS Guideline provides a set of recommendations concerning the information that should be used to evaluate the strength of an electronic search strategy.
Use the PRESS checklist when checking your systematic review search strategy:
The guideline was updated in 2016 and the full version can be found in PRESS Peer Review of Electronic Search Strategies: 2015 Guideline Explanation and Elaboration [PDF, 1.29MB] (page 39).