Systematic Reviews & Meta-analyses: Search

Guidance on conducting systematic reviews and meta-analyses.

Overview

A systematic review search aims for comprehensiveness in order to have the widest, relevant pool from which to select studies for analysis. This also helps to reduce potential bias by aiming to review and select from all known studies about the topic using your pre-established eligibility criteria, and following your study protocol. 

If you are new to advanced searching and would like to learn more, the University of Michigan's edX course on Advanced Literature Searching in the Health Sciences is a great place to start! For a quick lesson on searching basics, check out Monash University's tutorial on Developing a Search Strategy.

"Expert searchers are an important part of the systematic review team, crucial throughout the review process from the development of the proposal and research question to publicaiton." (McGowan & Sampson, 2005)

We use the PRESS Guidline and Checklist to consult with you on designing and then reviewing your systematic review search strategy. McGowan J, Sampson M, Salzwedel DM, Cogo E, Foerster V, Lefebvre C. PRESS Peer Review of Electronic Search Strategies: 2015 guideline statement. J Clin Epidemiol. 2016 Jul;75:40-6. http://www.sciencedirect.com/science/article/pii/S0895435616000585

Consult with a systematic review consulting librarian for the overall process, funding proposal considerations, protocol options, information sources, search methodology, and tools. If you are researching a discipline we are not familiar with, we will also connect you with a subject librarian in that area to locate appropriate sources, develop comprehensive searches, and access materials.

Book a consultation

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Request a consultation via email

srconsultation-g@vt.edu

  • In your email, let us know: (1) your current project research focus, planning stage, timeline, and goals and (2) 2-3 meting times that would work well for you during the next 2 weeks.

Systematic Review consulting librarians

  • Cozette Comer, Evidence Synthesis Librarian, Liaison Librarian: Statistics, Computational Modeling and Data Analytics; cozette@vt.edu

  • Kiri DeBose, Head, Veterinary Medicine Library & Liaison to Animal Sciences, kdebose@vt.edu

  • Ginny Pannabecker, Liaison Librarian: Biochemistry, Biocomplexity, Biological Sciences, Biomedical Engineering and Mechanics, Neuroscience, and Systems Biology; Assoc. Director, RCE, vpannabe@vt.edu

Selecting Databases to Seach

Note: As with all steps, check the guideline / protocol you are using to ensure you meet information source and search requirements.

When conducting a systematic review, it is important to create an effective search statement, and search multiple databases that cover your topic area to ensure you have conducted a comprehensive search to find as many relevant information sources as possible.

Use the "Subject Guides" provided by the University Libraries to locate key databases.  As these guides are intended to be used as starting points for research, consult with the subject librarian to determine what other databases would be useful for your topic.

When you select a database to choose, make sure to record:

  • Full name of the database
  • The provider of the database (e.g. EbscoHost, ProQuest, etc.)
  • Dates covered by VT's subscription to the database

When you conduct your search, make sure to record:

  • Date the search was conducted
  • Exact search terms used and how they were typed into the database
  • Fields searched in (if you searched in specific fields (title, abstract, subject), rather than the default general search)
  • Limiters or filters you included in your search, or that you added on the results page (publication date, article type, human subjects only, English language only, etc.)
  • Total number of search results

As access to database content by name, provider, and years covered vary by institution; and methods for conducting a search within a given database also vary, these pieces of information are crucial for other researchers to know, particularly if they are trying to replicate your search

Managing your search results:

  • Complete a search and document the information noted above
  • Export *all* search results to a citation manager (EndNote, Mendeley, Zotero) - sometimes you may have more results than a database will allow to be exported at once. In that case, keep track of the numbers you export and export sets of results until you have citations for all results in your citation manager. A caution - exporting full text is not helpful at this point - it may take up substantial space and you won't need full text for the first review study selection step of Title Abstract screening.
  • Decide on a method to identify the database source of the results (i.e. place them all in a folder or subfolder labeled with that database name, or conduct a 'global edit' for those references to add the database source name in each citation record
  • Repeat this process for each database search
  • Conduct any web searches planned and add results for these to your citation manager as well (you may need to manually enter website reports that don't have a citation export option)
  • Now you have all your initial results and you can record this as your starting study set number in your PRISMA diagram
  • Move on to Study Selection

Please note that the University Libraries and our vendors implement download limits that you may encounter when attempting to perform a comprehensive search. Find more information about these limits on our Collections Management Policy LibGuide. We know these limitations can be frustrating, but they are here to protect services for all users. If you encounter problems with these limits, please don't hesitate to reach out to us srconsultation-g@vt.edu.

Search Strategy Builder

Once you have developed keywords and terms that will help you identify and focus on more specific aspects of your topic, it’s helpful to create a search strategy that can be used to combine your terms using the Boolean operators AND and OR to search databases.

If you have not used Boolean operators in the past, or want to know what other tools you can use, read the information below.  If you have used them in the past, then use the Search Strategy Builder link below to create a search strategy. Make sure you put your synonyms in the like-colored columns for each concept you wish to tie together.

You can then copy and paste this search strategy into any of the databases as well as Google and Google Scholar.

Other cool tools

In addition to Boolean operators, here are a few other tools you can use as you build your search statements:

Truncation: 

Wouldn't it be great if there was a way to search for variations of a word so you didn't have to type OR all the time?  Good news, there is! The most common symbol used to add characters after a root word is the asterisks (*).  To use this, simply put the * at the end of your word, and the database will look for the root word, along with any letters that follow.  Be careful though, if your root word is too short, you'll get a lot of things that don't relate. For example:

forest* will find:

vet* will find:
  • forests
  • forest
  • forestry
  • foresters
  • vet
  • vets
  • veterinary
  • veterinarian(s)
  • veteran(s)
  • vetted
  • veto/vetoed/vetoes

There are other truncation symbols you can use within words as well. Check the "help" section of the database to see what other symbols are supported by that particular database and how they can be used.


Phrase Searching:

What if you need to search for a phrase?  You dictate that your terms must be found right next to each other and in the order you write them in simply by putting two or more words in quotation marks.  For example:

  • "Appalachian mountains"
  • "geographic information system"
  • "new river valley"


Nested Searches:

What if you want to use more than one Boolean operator and more than one of the above tools?  It is very easy to combine Boolean operators, but as this follows a logical system, you must include parentheses to dictate order of operations.  For example, while the following two searches use the same terms and the same Boolean operators in the exact same order, they'll return very different numbers of results based on how the search was interpreted (bold and colors demonstrate how it will be read by the system):

  • this search: "Blue Ridge mountains" OR "Appalachian Mountains" AND river* OR creek* OR stream* AND pollut*

would be interpreted as: "Blue Ridge mountains" OR "Appalachian Mountains" AND river* OR creek* OR stream* AND pollut*  

as the the above will look for records that have the phrase "Blue Ridge mountains" OR... anything that follows; it will look for records that have the phrase and term "Appalachian Mountains" AND river (and all variations: rivers, etc); it will look for records that have the term creek (and all variations: creeks, etc); and it will look for records that have the terms stream (and all variations: streams) and pollution/polluted/polluting (all variations of pollut*).

  • this search: ("Blue Ridge mountains" OR "Appalachian Mountains") AND (river* OR creek* OR stream*) AND pollut*

would be interpreted as: ("Blue Ridge mountains" OR "Appalachian Mountains") AND (river* OR creek* OR stream*) AND pollut*

as this search will look for records that have either (or both) of the phrases "Blue Ridge mountains"/"Appalachian mountains", but it also has to include either of the terms (and the variations of: river/creek/stream, and it has to include any of the variations of the term pollut* (polluted, polluting, pollution, etc) in order to come back in the results list.  

 

Citation Managers

The VT Libraries Citation Manager library guide provides an introduction to and links to video tutorials for major Citation Manager tools, such as Zotero, Mendeley, and EndNote

Grey Literature

It important to locate grey literature sources (conferences, government reports, associations) that also produce literature about your topic. 

Start with the databases, as many cover key conferences in a discipline, but search Google and Google Scholar as these are also excellent places to search for this type of information.  Look through the first 100-200 results to ensure that you haven't missed anything that would be relevant to your topic. 

Boolean Operators

Boolean operators are very powerful tools that follow a specific logic.  They dictate how you want your keywords to be searched, you just have to state how you want them to be used to interpret your terms. The two most commonly used in databases are:

  • AND: this operator allows you to combine different concepts together.  When you type in AND between terms, all of the terms you enter must be present in order for the record to be retrieved.  For example:
    • mountain AND culture AND virginia
  • OR: this operator allows you to find synonyms that relate to a particular concept.  Whey you type in OR between terms, as long as at least one of terms you enter is in record, the result will come  back.  For example:
    • river OR creek OR stream
       
  • NOT: this operators is exclusionary.  Most times you can write an effective search statement using OR and AND, but occasionally you may find too many results are still appearing, so you need to be more definitive on what should not be included. 
    • iris NOT flower

While many databases don't require for them to be capitalized, it is good practice to do so; plus you can quickly glance at your search statement and see where they are.  The above are the two most common, but there are other operators you can use. Check the "help" section of the database to see what other operators you can use that are supported by that particular database.