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Search Filters 101

Searching for accurate, evidence-based literature can be complicated. The good news is, most medical databases have developed filters to help you retrieve more precise results.

Search filters (also called hedges) are used to narrow a search and/or focus on a specific publication type, level of evidence, and/or subject area. Filters are constructed using specific database syntax (rules and commands). Search strategies are developed using rules and commands to search a variety of databases and interfaces, including PubMed, Ovid, EMBASE®, and CINAHL. (Nova Scotia Health Library Services, 2021)

Search filters are a quick and efficient way to search for information. They usually fall into two broad categories:

• Methodological: these help you locate specific types of studies (e.g. clinical trials, cohort studies, systematic reviews)
• Topic or subject: these cover various subjects or disciplines (e.g. palliative care, aging, lung cancer) 

(Curtin University Library, 2020)

It is important to recognize and identify the impact that using a particular filter may have on your search results. If a particular filter works well in a given context and does not appear to produce a high number of irrelevant results or exclude relevant items, by all means use it. However, you should be mindful that filters can alter what is retrieved from your search (Nova Scotia Health Library Services, 2021).

Several trusted databases, including PubMed, have developed filters to narrow search results by methodology, publication type or question category (e.g. therapy, diagnosis, etiology, prognosis, clinical prediction guides). Reviewing the step-by-step instructions for applying filters in PubMed is a helpful way to get started.  

Applying search filters in PubMed

Let’s work with a research question to see how search filters can assist you, when used properly, to obtain relevant results.

Example research question: Does exercise help improve back pain in adults? 

To help narrow down our results in PubMed we can apply the following filters after we have conducted our search:

• Age: Based on our example question, let’s use the age filter, specifically ‘adult’, to limit our results.
• Publication date: A good rule of thumb is to look for evidence published in the last five years (2017-2021), unless your research question specifies otherwise.
• Study/Publication type: You can filter to only retrieve a certain study type. For this example, let’s select systematic reviews. The best type of study may differ based on your research question.
• Language: You can limit results to a specific language, such as English or French only.

Applying these filters decreases our number of results from 7,000 to 34. Although this is a much more manageable number, it is important to be aware that potential results may be missed by applying filters.

It is recommended to use filters produced by trusted groups. For a detailed list of search filters produced by reliable groups, please visit Library Services’ Search Filters page.

Remember to be critical when using filters, so that you do not produce a high number of irrelevant results or exclude relevant items. For more information on search filters, be sure to check out our Searching guide for helpful tips. As always, reach out to Library Services with any questions or requests.

References:

Curtin University Library. (2020). Search Filters. Retrieved from https://libguides.library.curtin.edu.au/c.php?g=863554&p=6631322 

Nova Scotia Health Library Services. (2021). Searching. Retrieved from https://library.nshealth.ca/Searching

Amanda Andrews

Librarian Educator
Cape Breton Regional Hospital, Eastern Zone