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Systematic Reviews for the Health Sciences: Search strategy FAQs

Search strategy: Basic overview & FAQs

Overview:

For a systematic review, the goal of your search strategy is to be as inclusive as possible. 

In constructing your search strategy, you will need to go far beyond typical keyword searching. You will want to carefully identify synonyms and related words for each of the concepts that you search for, word variants for these terms, as well as any and all applicable controlled vocabulary terms (subject headings applied by the database) for the concept. It is recommended that you initially gather some of these by looking closely at exemplar articles--articles that clearly match the kind of article that you want to find more of.

This will likely be a highly iterative process, as you discover more and more terms that you should include, so it is recommended that you give yourself at least a month to develop search strategy. Also, remember that each database works a bit differently, so you will need to tailor your search strategy to the particulars of each database that you search in.

For a more detailed explanation of this process, we recommend reviewing these webinars recorded by UIC health sciences librarians in spring 2024:

We also have a tab on this guide that links to a separate guide on advanced search strategies which you might find useful.

Here is one detailed example of the potential components of conducting a systematic search of PubMed: http://libguides.vu.nl/PMroadmap/introduction

FAQs:

How many databases should I search?

This will depend on your topic. Some topics may necessitate searches in a dozen databases, but for others four databases might prove more appropriate. However, typically for health science topics, you should at least search PubMed, Embase, any other major databases for your specific discipline, and a database that will retrieve grey literature in your area. While there will likely be overlap in the coverage of the databases that you search, it is important to err on the side of gathering more records. 

How many records should I expect to retrieve?

While this will vary widely depending on your particular question, it is very common for a systematic review search strategy to result in the compilation of hundreds or thousands of records. In most reviews, only a very small percentage of the retrieved records are ultimately selected by the researchers as pertaining to their question and meeting all of their inclusion criteria. If you are not already using a citation manager, you will want to start using one. Please see the citation management tab of this guide for more information.

Are there some examples of search strategy that I can look at?

Yes, we recommend that you look at systematic reviews published in your field, and also to search the Cochrane Library and identify reviews there for a sense of best practices for this type of article. For Cochrane systematic reviews, the full search strategy will be contained within the appendices for the article.

If you would like help interpreting the search strategy for a database, please feel free to ask the liaison librarian for your subject.

What does it mean to document my search?

This means that you should document what databases you searched, what keywords and controlled vocabulary terms you used, how you put this together in terms of Boolean logic, and when you performed your search. In order to complete a PRISMA flowchart which is a standard component of a systematic review, you will also need to document how many articles you retrieved, before and after deduplicating your results.

Some databases, like PubMed, allow you to download your search strategy so that you can get a nice list of everything you searched, along with the number of results that were returned. Using an Excel spreadsheet can also be very useful for documenting this information. We have created a sample Excel spreadsheet with tabs and instructions that you might find useful that is available below.

Time saving tools for search formatting

Spreadsheet for formatting and compiling terms:

Here is a spreadsheet that can assist with formatting and compiling your subject headings and keywords.
NOTE: This spreadsheet may not work for older versions of Excel, including Excel 2016.

Here is a video on how this spreadsheet works: https://youtu.be/RL8EtF5Zhzs 

 

Tool for line by line searches

If you are using a line by line search approach for your search, you may need to OR together a long series of search numbers. It may be easier, and less prone to error, to copy and paste the numbers you need rather than manually typing them out.

Here is a file that works for PubMed or Embase, and one that works for CINAHL (on EBSCO):